Method for Manufacturing Light-Emitting Element and Deposition Apparatus

ABSTRACT

In order to provide a highly reliable organic EL element, a first step in which a deposition material is heated and vaporized in a deposition chamber in which the pressure is reduced and a second step in which a layer included in an EL layer is deposited in the deposition chamber are performed while exhaustion is performed and the partial pressure of water in the deposition chamber is measured with a mass spectrometer. Alternatively, the deposition chamber in the deposition apparatus includes a deposition material chamber and is connected to an exhaust mechanism. The deposition material chamber is separated from the deposition chamber by a sluice valve, includes a deposition material holding portion including a heating mechanism, and is connected to a mass spectrometer and an exhaust mechanism.

This application is a divisional of copending U.S. application Ser. No.13/870,246, filed on Apr. 25, 2013 which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing alight-emitting element using an organic electroluminescence (EL)phenomenon (hereinafter such a light-emitting element is also referredto as an organic EL element). The present invention also relates to adeposition apparatus used for manufacture of the organic EL element.

2. Description of the Related Art

An organic EL element has been actively researched and developed. In afundamental structure of the organic EL element, a layer containing alight-emitting organic compound (EL layer) is interposed between a pairof electrodes. The organic EL element has attracted attention as anext-generation flat panel display element owing to characteristics suchas feasibility of being thinner and lighter, high speed response toinput signals, and capability of direct current low voltage driving. Inaddition, a display using an organic EL element has a feature that it isexcellent in contrast and image quality, and has a wide viewing angle.Further, the organic EL element has been attempted to be applied as alight source such as a backlight of a liquid crystal display and alighting device because the organic EL element is a plane light source.

It is known that an organic compound or a metal material used for theorganic EL element easily reacts with impurities such as moisture andoxygen and easily deteriorates. The organic compound or the metalmaterial reacts with the impurities, whereby the lifetime of the organicEL element is largely shortened.

Therefore, in the case where an organic EL element is formed, atechnique by which a process of removing moisture and the like on asurface of a lower electrode, forming an EL layer and an upper electrodethereover, and sealing is performed without exposure to the atmosphereis required. For example, a multi-chamber or in-line thin film formationdevice by which formation of an EL layer, formation of an upperelectrode, and sealing can be performed is known (Patent Document 1).

REFERENCE Patent Document

-   [Patent Document 1] Japanese Published Patent Application    No.2001-102170

SUMMARY OF THE INVENTION

In the case where a deposited film included in an organic EL element isformed, by reduction in pressure in a deposition chamber, heating of adeposition material, or the like, impurities such as moisture in thedeposition material are exhausted to the deposition chamber. When thedeposited film is affected by these impurities, reliability of anorganic EL element to be manufactured is decreased (the lifetime isshortened).

One embodiment of the present invention is to provide a highly reliableorganic EL element. Another embodiment of the present invention is toprovide a deposition apparatus by which a highly reliable organic ELelement can be manufactured.

One embodiment of the present invention is a method for manufacturing alight-emitting element including a layer containing a light-emittingorganic compound (EL layer) between a pair of electrodes (organic ELelement). In the method, a first step in which moisture in a depositionmaterial placed in a deposition chamber is exhausted to the outside ofthe deposition chamber and a second step in which a layer included in anEL layer is deposited using the deposition material are performed whilethe partial pressure of water in the deposition chamber is measured witha mass spectrometer.

Even when the deposition material is heated for sufficient time in thefirst step, moisture is not sufficiently released from the depositionmaterial depending on the heating temperature in some cases. In thiscase, when the deposition is performed in the second step by vaporizingthe deposition material to deposit at a temperature higher than theheating temperature, moisture left in the deposition material isreleased from the deposition material. Therefore, in one embodiment ofthe present invention, the deposition material is heated and partlyvaporized in the first step. Thus, moisture in the deposition materialcan be sufficiently removed. Further, when the deposition material isvaporized in the second step, the amount of moisture released from thedeposition material is small.

While the partial pressure of water is measured with the massspectrometer, moisture in the deposition material is exhausted to theoutside of the deposition chamber; thus, it is confirmed that moistureis sufficiently removed from the deposition material and the depositionchamber, and then, the deposition can be performed. Consequently, alayer to be deposited can have less moisture, which enables a highlyreliable organic EL element to be manufactured.

One embodiment of the present invention is a method for manufacturing alight-emitting element including a layer containing a light-emittingorganic compound between a pair of electrodes over a substrate. In themethod, a first step in which a deposition material is heated andvaporized in a deposition chamber in which the pressure is reduced and asecond step in which a layer included in the layer containing alight-emitting organic compound is deposited in the deposition chamberafter the substrate is carried into the deposition chamber are performedwhile exhaustion is performed and the partial pressure of water in thedeposition chamber is measured with a mass spectrometer.

One embodiment of the present invention is a method for manufacturing alight-emitting element including a layer containing a light-emittingorganic compound between a pair of electrodes. In the method, a firststep in which a deposition material is heated and vaporized in adeposition chamber in which the pressure is reduced and a second step inwhich a layer included in the layer containing a light-emitting organiccompound is deposited in the deposition chamber are performed whileexhaustion is performed and the partial pressure of water in thedeposition chamber is measured with a mass spectrometer. At the start ofthe second step, the partial pressure of water is lower than the averagepartial pressure of water in the first step.

Note that in this specification and the like, vaporization includes notonly a phenomenon in which liquid changes to gas (evaporation orboiling) but also a phenomenon in which a solid directly changes to gas(sublimation).

Further, in this specification and the like, the partial pressure ismeasured with a mass spectrometer.

By the first step, moisture is released from the deposition material tothe inside of the deposition chamber, and the partial pressure of waterin the deposition chamber is increased. After that, reduction in theamount of moisture in the deposition material gradually reduces theamount of moisture released from the deposition material and moisture isexhausted to the outside of the deposition chamber, whereby the partialpressure of water in the deposition chamber is decreased. Then, afterthe partial pressure of water in the deposition chamber becomes lowerthan the average partial pressure of water in the first step, as thesecond step, the deposition material is heated and the layer included inthe EL layer is deposited.

In one embodiment of the present invention, the partial pressure ofwater in the deposition chamber can be checked with the massspectrometer in real time. Thus, a film included in an organic ELelement can be formed in a deposition chamber in which the partialpressure of water is sufficiently lowered.

In the above method for manufacturing an organic EL element, the averagepartial pressure of water in the second step is preferably lower thanthe average partial pressure of water in the first step.

In the above method for manufacturing an organic EL element, the heatingtemperature in the first step is preferably higher than or equal to theheating temperature in the second step.

The above method for manufacturing an organic EL element preferablyincludes a step of heating the deposition material at a temperaturelower than temperatures at which the deposition material is vaporized inthe deposition chamber in which the pressure is reduced before the firststep.

In particular, it is preferable that in the deposition chamber in whichthe pressure is reduced, the deposition material be heated at atemperature at which the deposition material is not vaporized, and afterthe partial pressure of water in the deposition chamber becomes themaximum value, the first step be started.

Since the deposition material is heated at a temperature higher than orequal to temperatures at which the deposition material is vaporized inthe first step, the deposition material is wasted owing to thevaporization. Further, by heating for a long time or at a hightemperature, the deposition material deteriorates in some cases.

Therefore, in the method for manufacturing a light-emitting elementaccording to one embodiment of the present invention, the depositionmaterial is heated at a temperature at which the deposition material isnot vaporized to remove moisture and then, the first step (heating thedeposition material at a temperature higher than or equal to thetemperatures at which the deposition material is vaporized) isperformed, whereby moisture which cannot be removed in the previousheating is removed from the deposition material. Thus, the amount of thedeposition material vaporized in the first step can be reduced, andconsumption of the deposition material can be suppressed. Further,deterioration of the deposition material, which is caused by long-timehigh temperature heating, can be suppressed.

The above method for manufacturing an organic EL element preferablyincludes a period during which the deposition material is not heated ora period during which the deposition material is heated at a temperaturelower than temperatures at which the deposition material is vaporizedbetween the first step and the second step.

In particular, in the first step after the partial pressure of water inthe deposition chamber becomes the maximum value, the method preferablyincludes a period during which the deposition material is not heated ora period during which the deposition material is heated at a temperaturelower than temperatures at which the deposition material is vaporized.

By stopping heating or setting the heating temperature to temperaturesat which the deposition material is not vaporized, vaporization of thedeposition material is stopped. Even when the heating is stopped (or theheating temperature is lowered), the deposition material is in ahigh-temperature state; thus, impurities such as moisture in thedeposition material are continuously removed. Further, impurities suchas moisture removed from the deposition material continue to beexhausted to the outside of the deposition chamber. Thus, the amount ofthe deposition material vaporized in the first step can be reduced, andconsumption of the deposition material can be suppressed. Further,deterioration of the deposition material, which is caused by long-timehigh temperature heating, can be suppressed.

In the above method for manufacturing an organic EL element, in thefirst step, by vaporization of the deposition material, a deposited filmis preferably formed over a substrate. The deposited film formed overthe substrate can be retrieved and reused as a deposition material.Consequently, the deposition material can be saved, which is preferable.

In the above method for manufacturing an organic EL element, the firststep is preferably performed while a wall of the deposition chamber isheated. In addition, the wall of the deposition chamber is preferablyheated before the first step.

The temperature of the wall of the deposition chamber is preferably highbecause impurities such as moisture are easily released from the walland exhausted to the outside of the deposition chamber.

In the above method for manufacturing an organic EL element, the wall ofthe deposition chamber is preferably cooled before the second step. Inaddition, the second step is preferably performed while the wall of thedeposition chamber is cooled.

When the temperature of the wall of the deposition chamber is set tolow, impurities such as moisture are hardly released from the wall. Thisis preferable because impurities such as moisture attached to the wallcan be prevented from being released from the wall and entering a filmduring deposition.

In the above method for manufacturing an organic EL element, the secondstep is preferably performed in the deposition chamber in which thepartial pressure of water (¹⁸H₂O) is lower than or equal to 1×10⁻⁴ Pa.

Here, a layer containing a material having high reactivity such aslithium easily reacts with impurities such as moisture. Further, when alight-emitting layer contains impurities, properties of thelight-emitting element tend to be remarkably affected. For thosereasons, in manufacture of such a layer, it is preferable that thesecond step be performed in a deposition chamber in which the partialpressure of water is lower than or equal to 2×10⁻⁵ Pa, more preferablylower than or equal to 1×10⁻⁵ Pa.

Further, oxygen is also an impurity affecting reliability of an organicEL element. Therefore, at the start of the second step, the partialpressure of oxygen atoms (¹⁶O) is preferably lower than the averagepartial pressure of oxygen atoms in the first step. The second step ispreferably performed in the deposition chamber in which the partialpressure of oxygen atoms is lower than or equal to 2×10⁻⁶ Pa.

In the above method for manufacturing an organic EL element, the massspectrometer is preferably a quadrupole mass spectrometer.

One embodiment of the present invention is a deposition apparatusincluding a deposition chamber which includes a deposition materialholding portion provided with a heating mechanism and is connected to anexhaust mechanism and a mass spectrometer and a control portion whichcontrols the heating mechanism in accordance with the partial pressureof water in the deposition chamber measured with the mass spectrometer.

One embodiment of the present invention is a deposition apparatusincluding a deposition chamber which includes a deposition materialholding portion provided with a heating mechanism, a mechanism whichheats a wall, and a mechanism which cools the wall, and is connected toan exhaust mechanism and a mass spectrometer.

In the deposition apparatus, the mass spectrometer is preferably aquadrupole mass spectrometer.

The deposition chamber included in the deposition apparatus according toone embodiment of the present invention includes a deposition materialchamber and is connected to an exhaust mechanism. The depositionmaterial chamber is separated from the deposition chamber by a sluicevalve, includes a deposition material holding portion provided with aheating mechanism, and is connected to a mass spectrometer and anexhaust mechanism.

While the partial pressure of water (¹⁸H₂O) in the deposition materialchamber is measured with the quadrupole mass spectrometer in a statewhere the sluice valve is closed, the deposition material is heated withthe heating mechanism. Impurities such as moisture are released from theheated deposition material and exhausted to the outside of thedeposition material chamber through the exhaust mechanism. Then, afterit is confirmed that the partial pressure of water in the depositionmaterial chamber is sufficiently low, the sluice valve is opened. Sincethe amount of moisture in the deposition material chamber issufficiently reduced, diffusion of impurities such as moisture into thedeposition chamber after the sluice valve is opened can be suppressed.

In a state where the sluice valve is opened, a deposited film is formedusing the deposition material over a substrate carried into thedeposition chamber. Since impurities such as moisture in the depositionmaterial are sufficiently reduced, the deposited film can have lessmoisture. Further, since the amount of moisture in the depositionmaterial chamber is sufficiently reduced and then the sluice valve isopened, moisture derived from the deposition material is hardlycontained in the deposition chamber. Consequently, the deposited filmformed in the deposition chamber can have less moisture, which enables ahighly reliable organic EL element to be manufactured.

One embodiment of the present invention is a deposition apparatusincluding a deposition chamber which is connected to a first exhaustmechanism and includes a deposition material chamber. The depositionmaterial chamber is separated from the deposition chamber by a sluicevalve and connected to a mass spectrometer and a second exhaustmechanism, and includes a deposition material holding portion providedwith a heating mechanism.

In the above deposition apparatus, the deposition material chamberpreferably includes a mechanism which heats an inner wall of thedeposition material chamber. In the above deposition apparatus, thedeposition material chamber preferably includes a mechanism which coolsthe inner wall of the deposition material chamber. In the abovedeposition apparatus, the deposition chamber preferably includes amechanism which heats the inner wall of the deposition chamber. In theabove deposition apparatus, the deposition chamber preferably includes amechanism which cools the inner wall of the deposition chamber. In theabove deposition apparatus, the deposition chamber is preferablyconnected to a mass spectrometer. In the above deposition apparatus, themass spectrometer connected to the deposition material chamber ispreferably a quadrupole mass spectrometer. In the above depositionapparatus, the mass spectrometer connected to the deposition chamber ispreferably a quadrupole mass spectrometer.

One embodiment of the present invention is a method for manufacturing alight-emitting element by the above deposition apparatus, thelight-emitting element including a layer containing a light-emittingorganic compound between a pair of electrodes. In the method, a firststep in which a deposition material held by the deposition materialholding portion is heated with the heating mechanism in the depositionmaterial chamber in which the pressure is reduced, which is separatedfrom the deposition chamber in which the pressure is reduced by closingthe sluice valve, and a second step in which the sluice valve is openedare performed while exhaustion is performed with the first exhaustmechanism and the second exhaust mechanism and a partial pressure ofwater in the deposition material chamber is measured with the massspectrometer; then, a layer included in the layer containing alight-emitting organic compound is deposited using the depositionmaterial over a substrate in the deposition chamber. At the start of thesecond step, the partial pressure of water in the deposition materialchamber is lower than the average partial pressure of water in the firststep.

One embodiment of the present invention is a method for manufacturing alight-emitting element by the above deposition apparatus, thelight-emitting element including a layer containing a light-emittingorganic compound between a pair of electrodes. In the method, a firststep in which a deposition material held by the deposition materialholding portion is heated with the heating mechanism in the depositionmaterial chamber in which the pressure is reduced, which is separatedfrom the deposition chamber in which the pressure is reduced by closingthe sluice valve, and a second step in which the sluice valve is openedare performed while exhaustion is performed with the first exhaustmechanism and the second exhaust mechanism and a partial pressure ofwater in the deposition material chamber is measured with the massspectrometer; then, a layer included in the layer containing alight-emitting organic compound is deposited using the depositionmaterial over a substrate in the deposition chamber. At the start of thesecond step, the partial pressure of water in the deposition materialchamber is lower than or equal to 1×10⁻⁴ Pa.

In the above method for manufacturing a light-emitting element, thetemperature of the heating mechanism in the first step is preferablyhigher than or equal to temperatures at which the deposition material isvaporized.

According to one embodiment of the present invention, while the partialpressure of water is measured with the mass spectrometer, moisture inthe deposition material is exhausted to the outside of the depositionchamber; thus, it is confirmed that moisture is sufficiently removedfrom the deposition material and the deposition chamber, and then, thedeposition is performed. Consequently, a layer to be deposited can haveless moisture, which enables a highly reliable organic EL element to beprovided.

In the deposition chamber included in the deposition apparatus accordingto one embodiment of the present invention, impurities such as moisturewhich are contained in the deposition material can be sufficientlyremoved in the deposition material chamber in advance; thus, diffusionof moisture derived from the deposition material into the depositionchamber can be suppressed. Consequently, the deposited film formed inthe deposition chamber can have less moisture, which enables a highlyreliable organic EL element to be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 shows an example of a deposition method;

FIGS. 2A and 2B illustrate examples of deposition apparatuses;

FIGS. 3A to 3C illustrate examples of deposition chambers;

FIGS. 4A to 4F illustrate examples of light-emitting elements;

FIGS. 5A to 5E illustrate examples of electronic devices;

FIGS. 6A and 6B illustrate examples of lighting devices;

FIGS. 7A and 7B illustrate light-emitting elements in Examples;

FIGS. 8A and 8B show the partial pressure of water in Example 1;

FIGS. 9A and 9B show the partial pressure of oxygen atoms in Example 1;

FIG. 10 shows the ratio of partial pressure in Example 1;

FIGS. 11A and 11B show luminance-current efficiency characteristics andvoltage-current characteristics of light-emitting elements of Example 1;

FIGS. 12A and 12B show emission spectra and results of reliability testsof light-emitting elements of Example 1;

FIG. 13 shows the partial pressure of water in Example 2;

FIGS. 14A and 14B show the partial pressure of water in Example 2;

FIGS. 15A and 15B show luminance-current efficiency characteristics andvoltage-current characteristics of light-emitting elements of Example 2;

FIG. 16 shows emission spectra of light-emitting elements of Example 2;

FIG. 17 shows results of reliability tests of light-emitting elements ofExample 2;

FIG. 18 shows the partial pressure of water in Example 3;

FIGS. 19A and 19B show the partial pressure of water in Example 3;

FIGS. 20A and 20B show luminance-current efficiency characteristics andvoltage-current characteristics of light-emitting elements of Example 3;

FIG. 21 shows emission spectra of light-emitting elements of Example 3;

FIG. 22 shows results of reliability tests of light-emitting elements ofExample 3;

FIG. 23 shows the partial pressure of water in Example 4;

FIGS. 24A and 24B show the partial pressure of water in Example 4;

FIGS. 25A and 25B luminance-current efficiency characteristics andvoltage-current characteristics of light-emitting elements of Example 4;

FIG. 26 shows emission spectra of light-emitting elements of Example 4;

FIG. 27 shows results of reliability tests of light-emitting elements ofExample 4;

FIG. 28 illustrates an example of a deposition chamber; and

FIGS. 29A to 29E illustrate an example of a deposition method.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described in detail withreference to the accompanying drawings. Note that the invention is notlimited to the following description, and it will be easily understoodby those skilled in the art that various changes and modifications canbe made without departing from the spirit and scope of the invention.Therefore, the invention should not be construed as being limited to thedescription in the following embodiments. Note that in the structures ofthe invention described below, the same portions or portions havingsimilar functions are denoted by the same reference numerals indifferent drawings, and description of such portions is not repeated.

Embodiment 1

In this embodiment, a deposition apparatus according to one embodimentof the present invention and a method for manufacturing a light-emittingelement according to one embodiment of the present invention aredescribed with reference to FIG. 1, FIGS. 2A and 2B, and FIGS. 3A to 3C.

In the method for manufacturing a light-emitting element according toone embodiment of the present invention, a first step of heating adeposition material to be vaporized in a deposition chamber in which thepressure is reduced and a second step of depositing a layer included inan EL layer in the deposition chamber are performed while exhaustion isperformed and the partial pressure of water in the deposition chamber ismeasured with a mass spectrometer. In addition, at the start of thesecond step, the partial pressure of water is lower than the averagepartial pressure of water in the first step.

Even when a deposition material is heated for sufficient time in thefirst step, moisture is not sufficiently released from the depositionmaterial depending on the heating temperature in some cases. In thiscase, when the deposition is performed in the second step by vaporizingthe deposition material to deposit at a temperature higher than theheating temperature, moisture left in the deposition material isreleased from the deposition material. Therefore, in the method formanufacturing a light-emitting element according to one embodiment ofthe present invention, the deposition material is heated and partlyvaporized in the first step. Thus, moisture in the deposition materialis exhausted to the inside of the deposition chamber and then to theoutside of the deposition chamber. Further, when the deposition materialis vaporized in the second step, the amount of moisture released fromthe deposition material is small.

Then, after the partial pressure of water in the deposition chamberbecomes lower than the average partial pressure of water in the firststep, in the second step, the deposition material is heated to depositthe layer included in the EL layer. Thus, the deposited layer can haveless moisture, which enables a highly reliable light-emitting element tobe manufactured.

<<Deposition Apparatus>>

First, a deposition apparatus is described with which a light-emittingelement can be manufactured by the method for manufacturing alight-emitting element according to one embodiment of the presentinvention.

For example, a light-emitting element can be manufactured with anin-line deposition apparatus or a multi-chamber deposition apparatus bythe method for manufacturing a light-emitting element according to oneembodiment of the present invention. The method for manufacturing alight-emitting element according to one embodiment of the presentinvention can be applied as long as at least one deposition chamber insuch a deposition apparatus is connected to a mass spectrometer and anexhaust mechanism and includes a heating mechanism for heating adeposition material.

Deposition apparatuses according to one embodiment of the presentinvention are illustrated in FIGS. 2A and 2B.

FIG. 2A illustrates an in-line deposition apparatus. The depositionapparatus in FIG. 2A includes a load lock chamber 101, a pretreatmentchamber 102, a plurality of deposition chambers (a deposition chamber103 a, a deposition chamber 103 b, a deposition chamber 103 c, adeposition chamber 103 d, a deposition chamber 103 e, and a depositionchamber 103 f), a delivery chamber 104, a posttreatment chamber 105, anda load lock chamber 106.

Each chamber includes an exhaust mechanism that can control its insidepressure. Further, each chamber may include a gas introduction mechanismthat can adjust the atmosphere of the inside.

The exhaust mechanisms are selected in accordance with usage ofrespective chambers. The exhaust mechanism may be one including a pumphaving an adsorption unit, such as a cryopump, a sputtering ion pump, ora titanium sublimation pump, one including a turbo molecular pumpprovided with a cold trap, or the like.

The load lock chamber 101 is connected to the exhaust mechanism. After asubstrate is transferred to the load lock chamber 101 which is underatmospheric pressure, the pressure of the inside of the chamber isreduced with the exhaust mechanism.

In the pretreatment chamber 102, heat treatment or the like can beperformed to remove impurities attached to the substrate.

In the plurality of deposition chambers, layers included in alight-emitting element can be deposited. In the deposition apparatusaccording to one embodiment of the present invention, at least onedeposition chamber has a structure where the chamber is connected to amass spectrometer and includes a heating mechanism for heating adeposition material. All the deposition chambers may have the structure.Each of the deposition chambers includes a buffer portion and isconnected to the adjacent deposition chamber with the buffer portionprovided therebetween. By providing the buffer portion, a phenomenon inwhich a deposition material blown off from the adjacent depositionchamber is mixed into the film during deposition can be prevented.

The delivery chamber 104 is connected to the exhaust mechanism. Throughthis chamber, the substrate placed in an environment under reducedpressure can be transferred to an environment under different pressure,e.g., atmospheric pressure.

The substrate provided with the light-emitting element is transferred tothe posttreatment chamber 105. Further, a sealing substrate or the likecan be transferred from the outside of the deposition apparatus. In theposttreatment chamber 105, the light-emitting element is sealed so asnot to be exposed to the atmosphere. The posttreatment chamber 105described in this embodiment includes two chambers, i.e., a substratestorage chamber and a sealing chamber. When the light-emitting elementis sealed, the sealing chamber is in an inert atmosphere or areduced-pressure atmosphere. The reduced-pressure atmosphere is, forexample, an atmosphere in which the pressure is lower than or equal to100 Pa, preferably lower than or equal to 1 Pa.

Then, the substrate with which sealing of the light-emitting element iscompleted can be transferred from the load lock chamber 106.

FIG. 2B illustrates a multi-chamber deposition apparatus. The depositionapparatus in FIG. 2B includes the load lock chamber 101, thepretreatment chamber 102, the plurality of deposition chambers (thedeposition chamber 103 a, the deposition chamber 103 b, the depositionchamber 103 c, the deposition chamber 103 d, the deposition chamber 103e, and the deposition chamber 103 f), the delivery chamber 104, theposttreatment chamber 105, the load lock chamber 106, a substratestandby chamber 107, a transfer chamber 108, and substrate transfermechanisms 109.

The load lock chamber 101 is connected to an exhaust mechanism 2001.After a substrate is transferred to the load lock chamber 101 which isunder atmospheric pressure, the pressure of the inside of the chamber isreduced with the exhaust mechanism 2001.

The pretreatment chamber 102 is connected to an exhaust mechanism 2002.In the pretreatment chamber 102, heat treatment or the like can beperformed to remove impurities attached to the substrate.

In the plurality of deposition chambers, layers included in alight-emitting element can be deposited. The deposition chambers areconnected to respective exhaust mechanisms (see exhaust mechanisms 2003a to 2003 f in FIG. 2B). In the deposition apparatus according to oneembodiment of the present invention, at least one deposition chamber hasa structure where the chamber is connected to a mass spectrometer andincludes a heating mechanism for heating a deposition material. All thedeposition chambers may have the structure.

As the mass spectrometer, a deflection (magnetic) mass spectrometer or anon-deflection mass spectrometer can be used. Examples of the deflectionmass spectrometer include a single-focusing mass spectrometer, adouble-focusing mass spectrometer, and a cycloidal mass spectrometer,and examples of the non-deflection mass spectrometer include atime-of-flight mass spectrometer, an omegatron, and a quadrupole massspectrometer.

As the mass spectrometer, a quadrupole mass spectrometer is preferablyused. A quadrupole mass spectrometer includes a small analysis unit andthus is easily placed in a desired position. In addition, a quadrupolemass spectrometer can scan at high speed and has high sensitivity in alow-mass region.

The delivery chamber 104 is connected to the exhaust mechanism 2004.Through this chamber, the substrate placed in an environment underreduced pressure can be transferred to an environment under differentpressure, e.g., atmospheric pressure.

The posttreatment chamber 105 is connected to an exhaust mechanism 2005.The substrate provided with the light-emitting element is transferred tothe posttreatment chamber 105. Further, a sealing substrate or the likecan be transferred from the outside of the deposition apparatus. In theposttreatment chamber 105, the light-emitting element is sealed so asnot to be exposed to the atmosphere. The posttreatment chamber 105 is inan inert atmosphere or a reduced-pressure atmosphere.

The load lock chamber 106 is connected to an exhaust mechanism 2006. Thesubstrate with which sealing of the light-emitting element is completedcan be transferred from the load lock chamber 106.

The substrate standby chamber 107 is connected to an exhaust mechanism2007. In the substrate standby chamber 107, the substrate in amanufacturing process of a light-emitting element can be in a standbystate.

The transfer chamber 108 is connected to an exhaust mechanism 2008. Thetransfer chamber 108 serves as a delivery chamber for transferring asubstrate from one chamber to another chamber.

In this embodiment, the load lock chamber 101 is a chamber in which asubstrate holder which stores an untreated substrate is placed, and theload lock chamber 106 is a chamber in which a substrate holder whichstores a treated substrate is placed. However, the deposition apparatusaccording to one embodiment of the present invention is not limitedthereto, and carrying out and carrying in of the substrate may beperformed with one load lock chamber.

Next, examples of the structure of the deposition chamber areillustrated in FIGS. 3A to 3C. Each of the deposition chambers in FIGS.3A to 3C includes a deposition material holding portion 111 providedwith a heating mechanism 113 and is connected to an exhaust mechanism119 and a quadrupole mass spectrometer 121.

FIG. 3A illustrates the case where the quadrupole mass spectrometer 121is provided on a sidewall of the deposition chamber. FIG. 3B illustratesthe case where the quadrupole mass spectrometer 121 is provided on theupper wall of the deposition chamber. The quadrupole mass spectrometer121 is preferably provided in the vicinity of a substrate holdingportion 125 or a substrate 123 as illustrated in FIGS. 3A and 3B, inwhich case, the amount of moisture in the vicinity of the substrate 123can be measured more accurately. Further, the shortest distance betweenthe quadrupole mass spectrometer 121 and the substrate holding portion125 is preferably shorter than that between the quadrupole massspectrometer 121 and the deposition material holding portion 111.

Alternatively, the quadrupole mass spectrometer 121 may be provided inthe vicinity of the exhaust mechanism 119 as illustrated in FIG. 3C.Note that at least one quadrupole mass spectrometer 121 is connected toone deposition chamber, and a plurality of quadrupole mass spectrometers121 may be connected to one deposition chamber.

In the deposition chambers in FIGS. 3A to 3C, while the partial pressureof water is measured with the quadrupole mass spectrometer 121, adeposition material can be heated with the heating mechanism 113 andvaporized. After it is confirmed that water in the deposition materialcan be sufficiently removed, a deposited film can be formed over thesubstrate; thus, the deposited film can have less moisture, whichenables a highly reliable light-emitting element to be manufactured.

In addition, with the use of the quadrupole mass spectrometer 121, thepartial pressure of oxygen atoms or the like may be measured.

As the exhaust mechanism connected to the deposition chamber, at leastthe exhaust mechanism 119 directly connected to the deposition chamberis provided. In addition, the exhaust mechanism 129 connected to thedeposition chamber through a pipe 127 may be provided. The exhaustmechanism 129 may be connected to another deposition chamber or the likethrough a pipe. In this case, the exhaust mechanism 119 can evacuate thedeposition chamber more highly than the exhaust mechanism 129.

FIGS. 3A to 3C each illustrate an example where the deposition material115 put in a container is held by the deposition material holdingportion 111. As a container for storing the deposition material, acrucible or a plate of a substance having small heat capacity (tungsten,molybdenum, or the like) can be used. With the use of the heatingmechanism 113, the deposition material 115 is heated. The heateddeposition material 115 is vaporized and deposited on the substrate 123.

Note that a plurality of deposition material holding portions 111 may beprovided in one deposition chamber. When different deposition materialsare set in the deposition material holding portions 111, a plurality ofsubstances can be vaporized and deposited at the same time (can beco-deposited) in the deposition chamber.

Further, FIGS. 3A to 3C each illustrate an example where the substrate123 and a mask are held by the substrate holding portion 125. Thesubstrate 123 (and the mask) is rotated by a substrate rotatingmechanism 135, so that uniformity of deposition can be increased. Thesubstrate rotating mechanism 135 may also serve as a substrate transfermechanism.

Further, the deposition chamber may include an imaging unit 133 such asa CCD camera. With the imaging unit 133, the positions of the substrate123 and the mask can be checked.

Furthermore, in the deposition chamber, the thickness of a filmdeposited on a substrate surface can be estimated from results ofmeasurements by a film thickness measurement mechanism 137. The filmthickness measurement mechanism 137 includes a crystal oscillator, forexample.

In order to control deposition of a vaporized deposition material, thedeposition apparatus preferably includes a shutter by which a substrateand a container are separated from each other until the vaporizationspeed of the deposition material is stabilized. FIGS. 3A to 3C eachillustrate an example where shutters 146 and 148 by which the substrateand the container are separated from each other are provided in thedeposition apparatus.

The deposition chamber preferably includes a mechanism which heats theinner wall or a mechanism which cools the inner wall. In thisembodiment, the deposition chamber includes a heating mechanism 117 anda cooling mechanism (not illustrated). The inner wall is preferablyformed using a material having high thermal conductivity. Further, asthe heating mechanism 117, it is possible to use a small tube heaterformed using a heating wire or the like. As the cooling mechanism, asmall tube to which a refrigerant is introduced or the like is used.Note that in order to perform the measurements accurately with thequadrupole mass spectrometer 121, it is preferable that a heatingmechanism or a cooling mechanism be not provided in the vicinity of aconnection with the quadrupole mass spectrometer 121.

When the temperature of the wall of the deposition chamber is increased,impurities such as moisture are easily released from the wall andexhausted to the outside of the deposition chamber. Accordingly, forexample, in the first step in the method for manufacturing alight-emitting element according to one embodiment of the presentinvention, the inner wall of the deposition chamber is preferably heatedwith a mechanism which heats the inner wall of the deposition chamber.

In contrast, when the temperature of the wall of the deposition chamberis lowered, impurities such as moisture are hardly released from thewall and diffusion of impurities into the deposition chamber can besuppressed. Accordingly, for example, in the second step in the methodfor manufacturing an organic EL element according to one embodiment ofthe present invention, the inner wall of the deposition chamber ispreferably cooled with a mechanism which cools the inner wall of thedeposition chamber. Consequently, entry of impurities to a film duringdeposition can be suppressed.

Further, the deposition apparatus according to one embodiment of thepresent invention may include a control portion connected to thequadrupole mass spectrometer 121 and the heating mechanism 113 includedin the deposition material holding portion 111. The control portion cancontrol the temperature of the heating mechanism 113 included in thedeposition material holding portion 111 in accordance with the partialpressure of water measured with the quadrupole mass spectrometer 121.

Specifically, a practitioner sets a condition of timing of proceedingfrom a certain step to the next step with the control portion inadvance. For example, the condition is set so that the control portionis operated to change the temperature of the heating mechanism 113 to atemperature for the next step after the value of the partial pressure ofwater measured with the quadrupole mass spectrometer 121 becomes themaximum value for predetermined minutes or after the value thereof isless than a certain value (for example, 1×10⁻⁴ Pa) is shown forpredetermined minutes. Thus, even when a practitioner does notcontinuously observe the apparatus or the mass spectrometer, the controlportion is automatically operated in a deposition chamber with thepartial pressure of water suitable to each step, which is preferable.Further, in order to control the whole deposition apparatus, the controlportion may be further connected to the substrate transfer mechanism orthe like.

<<Method for Manufacturing Light-Emitting Element>>

As described above, a feature of the method for manufacturing alight-emitting element according to one embodiment of the presentinvention lies in a step of forming a layer included in an EL layer. Oneembodiment of the present invention may be applied only to formation ofone layer included in an EL layer or formation of a plurality of layersincluded in an EL layer. One embodiment of the present invention isparticularly preferably applied to formation of all layers included inan EL layer. Examples of the structures and materials of alight-emitting element which can be manufactured according to oneembodiment of the present invention are described in Embodiment 3 indetail.

An example of the case where a first film included in the EL layer isdeposited in the deposition chamber in FIG. 3A is described below withreference to FIG. 1.

<Step S1: Placement of Deposition Material>

First, in the deposition chamber exposed to the atmosphere, a depositionmaterial is placed in the deposition material holding portion 111.Atmospheric components such as moisture and oxygen are attached to thisdeposition material. In other words, impurities with respect to anorganic EL element are contained.

<Step S2: Reduction in Pressure in Deposition Chamber>

Next, the pressure in the deposition chamber is reduced with the exhaustmechanism 119. Consequently, atmospheric components such as moisture andoxygen in the deposition chamber are exhausted to the outside of thedeposition chamber. Here, the pressure in the deposition chamber ispreferably lower than or equal to 10⁻⁴ Pa.

Then, before Step S3, the partial pressure of water in the depositionchamber is started to be measured with the, quadrupole mass spectrometer121 (corresponding to the origin in FIG. 1).

<Step S3: Heating of Deposition Material (at Low Temperature)>

Next, the deposition material 115 is heated with the heating mechanism113 included in the deposition material holding portion 111. Thetemperature of the heating mechanism 113 in Step S3 is set to atemperature at which the deposition material 115 is not vaporized. InFIG. 1, the highest temperature T2 in Step S3 is lower than temperaturesT1 at which the deposition material 115 is vaporized. Thus, thedeposition material 115 is not vaporized and impurities such as moistureand oxygen in the deposition material 115 are released to the inside ofthe deposition chamber. The impurities released to the inside of thedeposition chamber are exhausted to the outside of the depositionchamber through the exhaust mechanism 119.

The moisture removed from the deposition material 115 is diffused intothe deposition chamber; accordingly, the partial pressure of water inthe deposition chamber is temporarily increased. After that, the partialpressure of water is decreased due to reduction in the amount ofmoisture exhausted from the deposition material 115 to the inside of thedeposition chamber and the exhaust of moisture through the exhaustmechanism 119. The process preferably proceeds to Step S4 after thepartial pressure of water measured with the quadrupole mass spectrometer121 becomes the maximum value.

It is preferable that impurities which can be removed in Step S3 beremoved in advance because, in that case, the amount of a depositionmaterial vaporized at the time of removal of impurities can be reducedand the used amount of the deposition material can be reduced. Further,deterioration of the deposition material, which is caused by long-timehigh temperature heating, can be suppressed.

<Step S4: Heating of Deposition Material (at High Temperature)>

In Step S4, the deposition material 115 is heated at a highertemperature than that in Step S3. Specifically, the deposition material115 is heated at a temperature higher than the temperatures T1 at whichthe deposition material 115 is vaporized. The temperature of the heatingmechanism 113 is preferably higher than or equal to a temperature of theheating mechanism 113 (deposition temperature) in Step S6. As thetemperature of the deposition material 115 is higher, impurities such asmoisture and oxygen in the deposition material 115 are more easilyreleased. Thus, impurities which cannot be removed in Step S3 can beremoved from the deposition material 115. The impurities exhausted tothe inside of the deposition chamber are exhausted to the outside of thedeposition chamber through the exhaust mechanism 119.

Further, before Step S4, a substrate is preferably transferred to thedeposition chamber. After the substrate is transferred to the depositionchamber by a substrate transfer mechanism, Step S4 is conducted, wherebya vaporized deposition material is deposited on the substrate. Adeposited film on the substrate can be reused as a deposition material.Consequently, a loss of a deposition material due to the removal ofimpurities contained in the deposition material can be reduced, which ispreferable.

The moisture removed from the deposition material 115 is diffused intothe deposition chamber; accordingly, the partial pressure of water inthe deposition chamber is temporarily increased. After that, the partialpressure of water is decreased due to reduction in the amount ofmoisture exhausted from the deposition material 115 to the inside of thedeposition chamber and the exhaust of moisture through the exhaustmechanism 119. The process preferably proceeds to the next step afterthe partial pressure of water measured with the quadrupole massspectrometer 121 becomes the maximum value.

<Step S5: Stop of Heating of Deposition Material (at High Temperature)>

After that, the temperature of the heating mechanism 113 is set to atemperature at which the deposition material 115 is not vaporized orsublimed, or the heating is stopped. Thus, vaporization of thedeposition material 115 is stopped.

After Step S4, Step S6 may be performed without performing Step S5;however, even when the heating is stopped (or the temperature of theheating mechanism 113 is lowered), the deposition material 115 is in ahigh-temperature state and thus moisture in the deposition material 115is continuously removed. Further, moisture removed from the depositionmaterial 115 continues to be exhausted to the outside of the depositionchamber. Thus, the amount of a deposition material vaporized at the timeof removal of impurities can be reduced, and the used amount of thedeposition material can be reduced. Further, deterioration of thedeposition material, which is caused by long-time high temperatureheating, can be suppressed.

Note that in a period from Step S2 to Step S5, impurities exhausted tothe inside of the deposition chamber are adsorbed to the inner wall ofthe deposition chamber in some cases. Accordingly, it is preferable thatthe wall of the deposition chamber be heated with a mechanism whichheats the wall of the deposition chamber because, in that case, releaseof impurities attached to the wall of the deposition chamber and exhaustof the impurities to the outside of the deposition chamber can bepromoted. Heating of the wall of the deposition chamber may be performedat any time as long as it is performed between Step S2 and Step S6.

<Step S6: Formation of First Film>

The substrate 123 is carried in. A first film is formed over thesubstrate 123 in a deposition chamber in which the partial pressure ofwater is lower than the average partial pressure of water measured withthe quadrupole mass spectrometer 121 in Step S4.

A lower electrode of the light-emitting element is formed over thesubstrate 123 in advance. Further, another layer included in the ELlayer may be formed.

The average partial pressure of water in Step S6 is preferably lowerthan the average partial pressure of water in Step S4.

Further, Step S6 is preferably performed in a deposition chamber inwhich the partial pressure of water is lower than or equal to 1×10⁻⁴ Pa.

Here, a layer containing a material having high reactivity such aslithium easily reacts with water. Further, when a light-emitting layercontains impurities, properties of the light-emitting element tend to beremarkably affected. For those reasons, in the case where the first filmis a layer containing a material having high reactivity or alight-emitting layer, it is preferable that the deposition be performedin a deposition chamber in which the partial pressure of water is lowerthan or equal to 2×10⁻⁵ Pa, more preferably lower than or equal to1×10⁻⁵ Pa.

Further, reliability of a light-emitting element is decreased because ofnot only water but also oxygen. Therefore, it is preferable that thefirst film be formed over the substrate 123 in a deposition chamber inwhich the partial pressure of oxygen atoms is lower than the averagepartial pressure of oxygen atoms measured with the quadrupole massspectrometer 121 in Step S4. The average partial pressure of oxygenatoms in Step S6 is preferably lower than the average partial pressureof oxygen atoms in Step S4. In particular, Step S6 is preferablyconducted in a deposition chamber in which the partial pressure ofoxygen atoms is lower than or equal to 2×10⁻⁶ Pa.

Note that when impurities attached to the inner wall of the depositionchamber are released in Step S6, the impurities are diffused into thedeposition chamber and further mixed into the first film, so that alight-emitting element having a short lifetime is manufactured in somecases. Accordingly, it is preferable that Step S6 be performed while theinner wall of the deposition chamber is cooled with a mechanism whichcools the wall of the deposition chamber. Further, it is preferable thatthe inner wall of the deposition chamber be cooled before Step S6.

In the above-described manufacturing method, the layer included in theEL layer is formed after moisture is sufficiently removed from thedeposition material and the deposition chamber. Thus, the layer includedin the EL layer can have less moisture, which enables a highly reliablelight-emitting element to be manufactured.

This embodiment can be freely combined with any of the otherembodiments.

Embodiment 2

In this embodiment, a deposition apparatus according to one embodimentof the present invention and a method for manufacturing a light-emittingelement according to one embodiment of the present invention which aredifferent from those in Embodiment 1 are described with reference toFIGS. 2A and 2B, FIG. 28, and FIGS. 29A to 29E.

<<Deposition Apparatus>>

First, a deposition apparatus according to one embodiment of the presentinvention is described.

The deposition apparatus according to one embodiment of the presentinvention includes a deposition chamber which is connected to an exhaustmechanism and includes a deposition material chamber. The depositionmaterial chamber is separated from the deposition chamber by a sluicevalve and connected to a mass spectrometer and an exhaust mechanism, andincludes a deposition material holding portion provided with a heatingmechanism.

In the deposition chamber, impurities such as moisture in a depositionmaterial can be sufficiently removed in the deposition material chamberin advance; thus, diffusion of moisture derived from the depositionmaterial into the deposition chamber can be suppressed and a depositedfilm formed in the deposition chamber can have less moisture, whichenables a highly reliable light-emitting element to be manufactured.With the use of the deposition chamber, only one layer included in an ELlayer may be formed or a plurality of layers included in the EL layermay be formed. In particular, with the use of the deposition chamber,all the layers included in the EL layer are preferably formed.

The deposition apparatus according to one embodiment of the presentinvention includes at least one deposition chamber and may include aplurality of deposition chambers. Further, a deposition chamber having astructure different from the above structure may be further included.

Embodiment 1 can be referred to for details of the depositionapparatuses in FIGS. 2A and 2B according to one embodiment of thepresent invention.

Next, FIG. 28 exemplifies the structure of the deposition chamber whichis connected to the exhaust mechanism and includes the depositionmaterial chamber. Note that the deposition material chamber is separatedfrom the deposition chamber by the sluice valve and connected to themass spectrometer and the exhaust mechanism, and includes the depositionmaterial holding portion provided with the heating mechanism.

The deposition chamber in FIG. 28 is connected to an exhaust mechanism419 and includes a deposition material chamber 450.

As the exhaust mechanism connected to the deposition chamber, at leastthe exhaust mechanism 419 directly connected to the deposition chamberis provided. In addition, an exhaust mechanism 429 connected to thedeposition chamber through a pipe 427 may be provided. The exhaustmechanism 429 may be connected to another deposition chamber, thedeposition material chamber 450, or the like through a pipe. In thiscase, the exhaust mechanism 419 can evacuate the deposition chamber morehighly than the exhaust mechanism 429.

Further, FIG. 28 illustrates an example where a substrate 423 and a maskare held by a substrate holding portion 425. The substrate 423 (and themask) is rotated by a substrate rotating mechanism 435, so thatuniformity of deposition can be increased. The substrate rotatingmechanism 435 may also serve as a substrate transfer mechanism.

Further, the deposition chamber may include an imaging unit 433 such asa CCD camera. With the imaging unit 433, the positions of the substrate423 and the mask can be checked.

The deposition material chamber 450 is separated from the depositionchamber by a sluice valve 451 (a door valve, a gate valve, or the like)and connected to a quadrupole mass spectrometer 421 and an exhaustmechanism 439, and includes a deposition material holding portion 411provided with a heating mechanism 413.

As the exhaust mechanism connected to the deposition material chamber450, at least the exhaust mechanism 439 directly connected to thedeposition material chamber is provided.

FIG. 28 illustrates the case where the sluice valve 451 is closed. Byopening the sluice valve 451, the upper wall of the deposition materialchamber 450 does not hinder formation of the deposited film over thesubstrate. In the case where a sidewall of the deposition materialchamber 450 also hinders the formation, the sidewall of the depositionmaterial chamber 450 may have a structure in which the position thereofcan be moved so as not to hinder the formation. Further, by closing thesluice valve 451, the atmosphere of the deposition material chamber 450and the atmosphere of the deposition chamber can be different. Since thesluice valve 451 has high airtightness, in the case where the sluicevalve 451 is closed, the deposition material chamber 450 can be regardedas an isolated chamber (a sealed space).

FIG. 28 illustrates an example where the deposition material 415 put ina container is held by the deposition material holding portion 411. As acontainer for storing the deposition material, a crucible or a plate ofa substance having small heat capacity (tungsten, molybdenum, or thelike) can be used. With the use of the heating mechanism 413, thedeposition material 415 is heated.

Note that a plurality of deposition material holding portions may beprovided in one deposition chamber. One deposition material chamber mayinclude one deposition material holding portion or a plurality ofdeposition material holding portions. When different depositionmaterials are set in the deposition material holding portions, aplurality of substances can be vaporized and deposited at the same time(can be co-deposited) in the deposition chamber.

Further, the thickness of a film deposited on a substrate surface can beestimated from results of measurements by a film thickness measurementmechanism 437. The film thickness measurement mechanism 437 may includea crystal oscillator, for example. The film thickness measurementmechanism 437 may be provided outside the deposition material chamber450 (inside the deposition chamber).

Note that in order to control deposition of a vaporized depositionmaterial, a shutter 446 or 448 by which the substrate and the containerare separated from each other may be provided.

The deposition material chamber 450 preferably includes a mechanismwhich heats an inner wall or a mechanism which cools the inner wall. Inthis embodiment, the deposition material chamber 450 includes a heatingmechanism 444 and a cooling mechanism (not illustrated). The inner wallis preferably formed using a material having high thermal conductivity.It is possible to use a small tube heater formed using a heating wire orthe like as the heating mechanism 444. As the cooling mechanism, a smalltube to which a refrigerant is introduced or the like is used.

When the temperature of the wall of the deposition material chamber 450is increased, impurities such as moisture are easily released from thewall and exhausted to the outside of the deposition material chamber.Accordingly, the inner wall is preferably heated, for example, whenimpurities are exhausted to the outside of the deposition materialchamber 450 with the use of the exhaust mechanism 439 by closing thesluice valve 451 and heating the deposition material 415.

In contrast, when the temperature of the wall of the deposition materialchamber 450 is lowered, impurities such as moisture are hardly releasedfrom the wall and diffusion of impurities into the deposition materialchamber 450 and the deposition chamber can be suppressed. Therefore, forexample, the inner wall is preferably cooled when the sluice valve 451is opened and the deposited film is formed on the substrate. Thus, entryof impurities to a film during deposition can be suppressed.

Also the deposition chamber preferably includes a mechanism which heatsan inner wall or a mechanism which cools the inner wall. In thisembodiment, the deposition chamber includes a heating mechanism 417 anda cooling mechanism (not illustrated).

Further, the deposition chamber may be connected to a mass spectrometer.

In the deposition chamber in FIG. 28, while the partial pressure ofwater in the deposition material chamber 450 is measured with thequadrupole mass spectrometer 421 in a state where the sluice valve 451is closed, the deposition material 415 is heated with the heatingmechanism 413. Impurities such as moisture are released from the heateddeposition material 415 and exhausted to the outside of the depositionmaterial chamber 450 through the exhaust mechanism 439. Then, after itis confirmed that the partial pressure of water in the depositionmaterial chamber 450 is sufficiently low, the sluice valve 451 isopened. Since the amount of moisture in the deposition material chamber450 is sufficiently reduced, diffusion of impurities such as moistureinto the deposition chamber after the sluice valve 451 is opened can besuppressed.

In a state where the sluice valve 451 is opened, a deposited film isformed using the deposition material 415 over the substrate 423 carriedinto the deposition chamber. Since impurities such as moisture in thedeposition material 415 are sufficiently reduced in the depositionmaterial chamber 450, the deposited film can have less moisture.Further, since the amount of moisture in the deposition material chamber450 is sufficiently reduced and then the sluice valve 451 is opened,moisture derived from the deposition material is hardly contained in thedeposition chamber. Consequently, the deposited film formed in thedeposition chamber can have less moisture, which enables a highlyreliable organic EL element to be manufactured.

In addition, with the quadrupole mass spectrometer 421, the partialpressure of oxygen atoms (¹⁶O) or the like in the deposition materialchamber 450 may be measured.

Further, the deposition apparatus according to one embodiment of thepresent invention may include a control portion connected to thequadrupole mass spectrometer 421 and the heating mechanism 413 includedin the deposition material holding portion 411. The control portion cancontrol the temperature of the heating mechanism 413 included in thedeposition material holding portion 411 in accordance with the partialpressure of water measured with the quadrupole mass spectrometer 421.

Specifically, a practitioner sets a condition of timing of proceedingfrom a certain step to the next step with the control portion inadvance. For example, the condition is set so that the control portionis operated to change the temperature of the heating mechanism 413 to atemperature for the next step after the value of the partial pressure ofwater measured with the quadrupole mass spectrometer 421 becomes themaximum value for predetermined minutes or after the value thereof isless than a certain value (for example, 1×10⁻⁴ Pa) is shown forpredetermined minutes. Thus, even when a practitioner does notcontinuously observe the apparatus or the mass spectrometer, the controlportion is automatically operated in a deposition material chamber withthe partial pressure of water suitable to each step, which ispreferable. Further, in order to control the whole deposition apparatus,the control portion may be further connected to the sluice valve 451, asubstrate transfer mechanism, or the like.

<<Method for Manufacturing Light-Emitting Element>>

An example of the case where a first film included in an EL layer isdeposited in the deposition chamber in FIG. 28 is described below.Examples of the structure and material of a light-emitting elementmanufactured according to one embodiment of the present invention aredescribed in Embodiment 3 in detail.

<Step S1: Placement of Deposition Material>

First, in the deposition material chamber 450 exposed to the atmosphere,the deposition material 415 is placed in the deposition material holdingportion 411. Atmospheric components such as moisture and oxygen areattached to this deposition material 415. In other words, impuritieswith respect to an organic EL element are contained.

Note that in the case where the deposition chamber and the depositionmaterial chamber 450 are under reduced pressure, the deposition materialchamber 450 is preferably exposed to the atmosphere after the sluicevalve 451 is closed. By closing the sluice valve 451 and exposing onlythe deposition material chamber 450 to the atmosphere, contamination ina wide space due to exposure of the whole deposition chamber to theatmosphere can be prevented. Compared to the case where the wholedeposition chamber is exposed to the atmosphere and then evacuated toreduce the pressure thereof, the case where only the deposition materialchamber 450 is exposed to the atmosphere and evacuated to reduce thepressure thereof is preferable because the required time is short.

<Step S2: Reduction in Pressure in Deposition Material Chamber>

Next, the pressure in the deposition material chamber 450 is reducedwith the exhaust mechanism 439. Consequently, atmospheric componentssuch as moisture and oxygen in the deposition material chamber 450 areexhausted to the outside of the deposition material chamber 450. Here,the pressure in the deposition material chamber 450 is preferably lowerthan or equal to 10⁻⁴ Pa.

Then, before Step S3, the partial pressure of water in the depositionmaterial chamber 450 is started to be measured with the quadrupole massspectrometer 421.

<Step S3: Heating of Deposition Material>

Next, the deposition material 415 is heated with the heating mechanism413 included in the deposition material holding portion 411. Thus,impurities such as moisture and oxygen in the deposition material 415are released to the inside of the deposition material chamber 450. Theimpurities released to the inside of the deposition material chamber 450are exhausted to the outside of the deposition material chamber 450through the exhaust mechanism 439.

The moisture removed from the deposition material 415 is diffused intothe deposition material chamber 450; accordingly, the partial pressureof water in the deposition material chamber 450 is temporarilyincreased. After that, the partial pressure of water is decreased due toreduction in the amount of moisture exhausted from the depositionmaterial 415 to the inside of the deposition material chamber 450 andexhaust of moisture through the exhaust mechanism 439.

At this time, the temperature of the heating mechanism 413 is preferablyhigher than or equal to temperatures at which the deposition material415 is vaporized, more preferably higher than or equal to thetemperature of the heating mechanism 413 (deposition temperature) inStep S4. As the temperature of the deposition material 415 is higher,impurities such as moisture and oxygen in the deposition material 415are easily released. Therefore, in Step S3, heating is performed at atemperature higher than or equal to the temperature of the heatingmechanism 413 in Step S4, so that release of impurities from thedeposition material during deposition can be suppressed.

In particular, it is preferable that impurities which can be removed ata temperature lower than or equal to the temperatures at which thedeposition material 415 is vaporized be removed, and then thetemperature be increased to higher than or equal to the temperature atwhich the deposition material 415 is vaporized. The amount of adeposition material vaporized at the time of the removal of impuritiescan be reduced, and the used amount of the deposition material can bereduced. Further, the deterioration of the deposition material, which iscaused by long-time high temperature heating, can be suppressed.

Further, the deposition material vaporized in Step S3 is attached to theinner wall of the deposition material chamber 450 or the sluice valve451 in some cases. When the inner wall or the sluice valve has a layeredstructure and a layer to which the deposition material is attached canbe detached at the time of exposure to the atmosphere, a film attachedto the layer can be reused as a deposition material. Consequently, aloss of a deposition material due to the removal of impurities containedin the deposition material can be reduced, which is preferable

Before Step S4, vaporization of the deposition material 415 ispreferably stopped by setting the temperature of the heating mechanism413 to a temperature at which the deposition material 415 is notvaporized or sublimed or by stopping heating.

Even when the heating is stopped (or the temperature of the heatingmechanism 413 is lowered), the deposition material 415 is in ahigh-temperature state and thus moisture in the deposition material 415is continuously removed. Further, moisture removed from the depositionmaterial 415 continues to be exhausted to the outside of the depositionmaterial chamber 450. Thus, the amount of a deposition materialvaporized at the time of removal of impurities can be reduced, and theused amount of the deposition material can be reduced. Further,deterioration of the deposition material, which is caused by long-timehigh temperature heating, can be suppressed.

Note that in a period from Step S2 to Step S3, impurities exhausted tothe inside of the deposition material chamber 450 are adsorbed to theinner wall of the deposition material chamber 450 in some cases.Accordingly, it is preferable that the wall of the deposition materialchamber 450 be heated with a mechanism which heats the wall of thedeposition material chamber 450 because, in that case, release ofimpurities attached to the wall of the deposition material chamber 450and exhaust of the impurities to the outside of the deposition materialchamber 450 can be promoted. Heating of the wall of the depositionmaterial chamber 450 may be performed at any time as long as it isperformed between Step S2 and Step S3.

Before Step S4, the inside of the deposition chamber is set to reducedpressure. Here, the pressure in the deposition chamber is preferablylower than or equal to 10⁻⁴ Pa.

The substrate 423 is carried in. A lower electrode of the light-emittingelement is formed over the substrate 423 in advance. Further, anotherlayer included in the EL layer may be formed.

<Step S4: Opening of Sluice Valve>

It is confirmed that the partial pressure of water measured with thequadrupole mass spectrometer 421 is sufficiently low, and then, thesluice valve 451 is opened.

For example, it is preferable that the sluice valve 451 be opened afterthe partial pressure of water becomes lower than the average partialpressure of water in Step S3. Alternatively, it is preferable that thesluice valve 451 be opened after the partial pressure of water becomeslower than or equal to 1×10⁻⁴ Pa.

Here, a layer containing a material having high reactivity such aslithium easily reacts with water. Further, when a light-emitting layercontains impurities, properties of the light-emitting element tend to beremarkably affected. For those reasons, in the case where the first filmis a layer containing a material having high reactivity or alight-emitting layer, it is preferable that the sluice valve 451 beopened after the partial pressure of water becomes lower than or equalto 2×10⁻⁵ Pa, more preferably lower than or equal to 1×10⁻⁵ Pa.

Further, reliability of a light-emitting element is decreased because ofnot only water but also oxygen. Therefore, the sluice valve 451 ispreferably opened when the partial pressure of oxygen atoms is lowerthan the average partial pressure of oxygen atoms measured with thequadrupole mass spectrometer 421 in Step S3.

Note that when impurities attached to the inner wall of the depositionmaterial chamber 450 are released after Step S4, the impurities may bediffused into the deposition chamber and further mixed into the firstfilm, which may result in manufacture of a light-emitting element havinga short lifetime. Accordingly, it is preferable that steps after Step S4be performed while the inner wall of the deposition material chamber 450is cooled with a mechanism which cools the wall of the depositionmaterial chamber 450. Further, before Step S4, the inner wall of thedeposition material chamber 450 is preferably cooled.

In the above-described manufacturing method, the sluice valve 451 isopened after moisture is sufficiently removed from the depositionmaterial and the deposition material chamber 450. Thus, diffusion ofmoisture derived from the deposition material into the depositionchamber can be suppressed and a deposited film formed in the depositionchamber can have less moisture, which enables a highly reliablelight-emitting element to be manufactured.

FIGS. 29A to 29E each illustrate a structure of a deposition chamber,which is different from that in FIG. 28, and a method for manufacturinga light-emitting element with the deposition chamber.

The deposition material chamber 450 in FIG. 29A includes a depositionmaterial 415 a and a deposition material 415 b each held by a depositionmaterial holding portion. Further, a deposition chamber 460 includes,outside the deposition material chamber 450, a deposition material 415 cand a deposition material 415 d each held by a deposition materialholding portion. Note that the deposition materials 415 a to 415 d maybe the same material or different materials.

By closing the sluice valve 451, while keeping the pressure of theoutside of the deposition material chamber 450 under reduced pressure,only the inside of the deposition material chamber 450 can be exposed tothe atmosphere.

The deposition material chamber 450 is connected to the exhaustmechanism 439 and the quadrupole mass spectrometer 421.

Thus, as illustrated in FIG. 29B, while a deposited film is formed usingthe deposition material 415 c and the deposition material 415 d over thesubstrate 423 a, impurities such as moisture in the deposition material415 a and the deposition material 415 b can be removed by heating thedeposition material 415 a and the deposition material 415 b.

When the remaining amount of the deposition material 415 c and theremaining amount of the deposition material 415 d become small, heatingis stopped. Note that movement of a substrate 423 b over which adeposited film is formed next is also stopped. Then, the sluice valve451 is opened (FIG. 29C). In this case, not only the sluice valve 451but also the sidewall of the deposition material chamber 450 is movable.

Then, a deposited film is formed over the substrate 423 b with the useof the deposition material 415 a and the deposition material 415 b fromwhich impurities are sufficiently removed in the deposition materialchamber 450 (FIG. 29D).

Note that in the case where the deposition material 415 c and thedeposition material 415 d are provided in another deposition materialchamber, after a sluice valve is closed, the inside of the depositionmaterial chamber can be exposed to the atmosphere and replacement ofmaterials or the like can be performed (FIG. 29E).

As described above, a deposition apparatus to which one embodiment ofthe present invention is applied is preferable because a deposited filmcan be formed in parallel with removal of impurities such as moisture ina deposition material and thus, a light-emitting element can beefficiently manufactured.

Further, even when a small amount of a deposition material is placed inone deposition material holding portion, the process efficiency of anapparatus is not decreased, so that deterioration of the depositionmaterial due to long-time heating or the like can be suppressed, whichis preferable.

This embodiment can be freely combined with any of the otherembodiments.

Embodiment 3

In this embodiment, examples of a light-emitting element manufacturedaccording to one embodiment of the present invention are described withreference to FIGS. 4A to 4F.

Each of the light-emitting elements shown in this embodiment includes apair of electrodes (a first electrode and a second electrode) and an ELlayer(s) provided between the pair of electrodes. One of the pair ofelectrodes serves as an anode and the other serves as a cathode. The ELlayer(s) includes at least a light-emitting layer. Among the ELlayer(s), a layer formed using a material that can be deposited can beformed by application of one embodiment of the present invention. As thematerial that can be deposited, for example, a low-molecular compoundand an inorganic compound can be given.

In a light-emitting element manufactured by application of oneembodiment of the present invention, the amount of contained impuritiessuch as moisture is reduced. Therefore, a highly reliable light-emittingelement can be obtained.

One embodiment of the present invention can be applied to the case wherea light-emitting element with any of a top emission structure, a bottomemission structure, and a dual emission structure is manufactured.

A light-emitting element illustrated in FIG. 4A includes an EL layer 203between a first electrode 201 and a second electrode 205. In thisembodiment, the first electrode 201 serves as the anode, and the secondelectrode 205 serves as the cathode.

When a voltage higher than the threshold voltage of the light-emittingelement is applied between the first electrode 201 and the secondelectrode 205, holes are injected to the EL layer 203 from the firstelectrode 201 side and electrons are injected to the EL layer 203 fromthe second electrode 205 side. The injected electrons and holes arerecombined in the EL layer 203 and a light-emitting substance containedin the EL layer 203 emits light.

The EL layer 203 includes at least a light-emitting layer, as describedabove. In addition to the light-emitting layer, the EL layer 203 mayfurther include one or more layers containing any of a substance with ahigh hole-injection property, a substance with a high hole-transportproperty, a hole-blocking material, a substance with a highelectron-transport property, a substance with a high electron-injectionproperty, a substance with a bipolar property (a substance with a highelectron- and hole-transport property), and the like.

For the EL layer 203, either a low molecular compound or a highmolecular compound can be used, and an inorganic compound may also beused.

A specific example of a structure of the EL layer 203 is illustrated inFIG. 4B. In the EL layer 203 illustrated in FIG. 4B, a hole-injectionlayer 301, a hole-transport layer 302, a light-emitting layer 303, anelectron-transport layer 304, and an electron-injection layer 305 arestacked in this order from the first electrode 201 side.

A light-emitting element illustrated in FIG. 4C includes the EL layer203 between the first electrode 201 and the second electrode 205, andfurther includes an intermediate layer 207 between the EL layer 203 andthe second electrode 205.

A specific example of a structure of the intermediate layer 207 isillustrated in FIG. 4D. The intermediate layer 207 includes at least acharge-generation region 308. In addition to the charge-generationregion 308, the intermediate layer 207 may further include anelectron-relay layer 307 and an electron-injection buffer layer 306.

When a voltage higher than the threshold voltage of the light-emittingelement is applied between the first electrode 201 and the secondelectrode 205, holes and electrons are generated in thecharge-generation region 308, and the holes move into the secondelectrode 205 and the electrons move into the electron-relay layer 307.The electron-relay layer 307 has a high electron-transport property andimmediately transfers the electrons generated in the charge-generationregion 308 to the electron-injection buffer layer 306. Theelectron-injection buffer layer 306 reduces a barrier to electroninjection into the EL layer 203, so that the efficiency of the electroninjection into the EL layer 203 is increased. Thus, the electronsgenerated in the charge-generation region 308 are injected into the LUMOlevel of the EL layer 203 through the electron-relay layer 307 and theelectron-injection buffer layer 306.

In addition, the electron-relay layer 307 can prevent reaction at theinterface between a substance contained in the charge-generation region308 and a substance contained in the electron-injection buffer layer306. Thus, it is possible to prevent interaction such as damaging thefunctions of the charge-generation region 308 and the electron-injectionbuffer layer 306.

As illustrated in light-emitting elements in FIGS. 4E and 4F, aplurality of EL layers may be stacked between the first electrode 201and the second electrode 205. In this case, the intermediate layer 207is preferably provided between the stacked EL layers. For example, thelight-emitting element illustrated in FIG. 4E includes the intermediatelayer 207 between a first EL layer 203 a and a second EL layer 203 b.The light-emitting element illustrated in FIG. 4F includes n EL layers(n is a natural number of 2 or more), and the intermediate layer 207 isprovided between the stacked EL layers.

The following will show behaviors of electrons and holes in theintermediate layer 207 between the EL layer 203(m) and the EL layer203(m+1). When a voltage higher than the threshold voltage of thelight-emitting element is applied between the first electrode 201 andthe second electrode 205, holes and electrons are generated in theintermediate layer 207, and the holes move into the EL layer 203(m+1)provided on the second electrode 205 side and the electrons move intothe EL layer 203(m) provided on the first electrode 201 side. The holesinjected into the EL layer 203(m+1) are recombined with the electronsinjected from the second electrode 205 side, so that a light-emittingsubstance contained in the EL layer 203(m+1) emits light. Further, theelectrons injected into the EL layer 203(m) are recombined with theholes injected from the first electrode 201 side, so that alight-emitting substance contained in the EL layer 203(m) emits light.Thus, the holes and electrons generated in the intermediate layer 207cause light emission in the respective EL layers.

Note that the EL layers can be provided in contact with each other aslong as the same structure as the intermediate layer is formedtherebetween. For example, when the charge-generation region is formedover one surface of an EL layer, another EL layer can be provided incontact with the surface.

Further, by forming EL layers to emit light of different colors fromeach other, a light-emitting element as a whole can provide lightemission of a desired color. For example, by forming a light-emittingelement having two EL layers such that the emission color of the firstEL layer and the emission color of the second EL layer are complementarycolors, the light-emitting element can provide white light emission as awhole. Note that the word “complementary” means color relationship inwhich an achromatic color is obtained when colors are mixed. That is,white light emission can be obtained by mixture of light from materialswhose emission colors are complementary colors. This can be applied to alight-emitting element having three or more EL layers.

FIGS. 4A to 4F can be used in an appropriate combination. For example,the intermediate layer 207 can be provided between the second electrode205 and the EL layer 203(n) in FIG. 4F.

Examples of materials which can be used for each layer will be describedbelow. Note that each layer is not limited to a single layer, but may bea stack of two or more layers.

<Anode>

The electrode serving as the anode (the first electrode 201) can beformed using one or more kinds of conductive metals, alloys, conductivecompounds, and the like. In particular, it is preferable to use amaterial with a high work function (4.0 eV or more). Examples includeindium tin oxide (ITO), indium tin oxide containing silicon or siliconoxide, indium zinc oxide, indium oxide containing tungsten oxide andzinc oxide, graphene, gold, platinum, nickel, tungsten, chromium,molybdenum, iron, cobalt, copper, palladium, and a nitride of a metalmaterial (e.g., titanium nitride).

When the anode is in contact with the charge-generation region, any of avariety of conductive materials can be used regardless of their workfunctions; for example, aluminum, silver, an alloy containing aluminum,or the like can be used.

<Cathode>

The electrode serving as the cathode (the second electrode 205) can beformed using one or more kinds of conductive metals, alloys, conductivecompounds, and the like. In particular, it is preferable to use amaterial with a low work function (3.8 eV or less). Examples includealuminum, silver, an element belonging to Group 1 or 2 of the periodictable (e.g., an alkali metal such as lithium or cesium, an alkalineearth metal such as calcium or strontium, or magnesium), an alloycontaining any of these elements (e.g., Mg—Ag or Al—Li), a rare earthmetal such as europium or ytterbium, and an alloy containing any ofthese rare earth metals.

When the cathode is in contact with the charge-generation region, any ofa variety of conductive materials can be used regardless of their workfunctions; for example, ITO or indium tin oxide containing silicon orsilicon oxide can be used.

The light-emitting element may have a structure in which one of theanode and the cathode is formed using a conductive film that transmitsvisible light and the other is formed using a conductive film thatreflects visible light, or a structure in which both the anode and thecathode are formed using conductive films that transmit visible light.

The conductive film that transmits visible light can be formed using,for example, indium oxide, ITO, indium zinc oxide, zinc oxide, or zincoxide to which gallium is added. Alternatively, a film of a metalmaterial such as gold, platinum, nickel, tungsten, chromium, molybdenum,iron, cobalt, copper, palladium, or titanium, or a nitride of any ofthese metal materials (e.g., titanium nitride) formed thin so as to havea light-transmitting property can be used. Further alternatively,graphene or the like may be used.

The conductive film that reflects visible light can be formed using, forexample, a metal material such as aluminum, gold, platinum, silver,nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, orpalladium; an aluminum-containing alloy (aluminum alloy) such as analloy of aluminum and titanium, an alloy of aluminum and nickel, or analloy of aluminum and neodymium; or a silver-containing alloy such as analloy of silver and copper. An alloy of silver and copper is preferablebecause of its high heat resistance. Further, lanthanum, neodymium, orgermanium may be added to the metal material or the alloy.

The electrodes may be formed separately by a vacuum evaporation methodor a sputtering method. Alternatively, when a silver paste or the likeis used, a coating method or an inkjet method may be used.

<Hole-Injection Layer 301>

The hole-injection layer 301 contains a substance with a highhole-injection property.

Examples of the substance with a high hole-injection property includemetal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide,tungsten oxide, and manganese oxide, phthalocyanine-based compounds suchas phthalocyanine (H₂Pc) and copper(II) phthalocyanine (CuPc), and thelike.

Alternatively, it is possible to use a high molecular compound such aspoly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine)(abbreviation: PVTPA), or a high molecular compound to which acid isadded, such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonicacid) (PEDOT/PSS).

The hole-injection layer 301 may serve as the charge-generation region.When the hole-injection layer 301 in contact with the anode serves asthe charge-generation region, a variety of conductive materials can beused for the anode regardless of their work functions. Materialscontained in the charge-generation region will be described later.

<Hole-Transport Layer 302>

The hole-transport layer 302 contains a substance with a highhole-transport property.

The substance with a high hole-transport property is preferably asubstance with a property of transporting more holes than electrons, andis especially preferably a substance with a hole mobility of 10⁻⁶ cm²/Vsor more. For example, it is possible to use any of a variety ofcompounds such as an aromatic amine compound such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD) or 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP), a carbazole derivative such as4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA), or9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:PCzPA), an aromatic hydrocarbon compound such as2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),9,10-di(2-naphthyl)anthracene (abbreviation: DNA), or9,10-diphenylanthracene (abbreviation: DPAnth), or a high molecularcompound such as PVK or PVTPA.

<Light-Emitting Layer 303>

For the light-emitting layer 303, a light-emitting substance such as afluorescent compound, which exhibits fluorescence, or a phosphorescentcompound, which exhibits phosphorescence, can be used.

Examples of the fluorescent compound that can be used for thelight-emitting layer 303 includeN,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCAPA), and rubrene.

Examples of the phosphorescent compound that can be used for thelight-emitting layer 303 include metallo-organic complexes such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium (III)picolinate(abbreviation: FIrpic), tris(2-phenylpyridinato-N,C^(2′))iridium(III)(abbreviation: Ir(ppy)₃), and(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: Ir(mppr-Me)₂(acac)).

Note that the light-emitting layer 303 may have a structure in which anyof the above light-emitting substances (a guest material) is dispersedin another substance (a host material). As the host material, a varietyof kinds of materials can be used, and it is preferable to use asubstance which has a lowest unoccupied molecular orbital level (LUMOlevel) higher than that of the guest material and has a highest occupiedmolecular orbital level (HOMO level) lower than that of the guestmaterial.

With a structure in which a guest material is dispersed in a hostmaterial, crystallization of the light-emitting layer 303 can besuppressed. Further, concentration quenching due to high concentrationof the guest material can be suppressed.

As the host material, the above-described substance having a highhole-transport property (e.g., an aromatic amine compound or a carbazolederivative), a substance having a high electron-transport property(e.g., a metal complex having a quinoline skeleton or a benzoquinolineskeleton or a metal complex having an oxazole-based ligand or athiazole-based ligand), which will be described later, or the like canbe used. Specifically, a metal complex such astris(8-quinolinolato)aluminum(III) (abbreviation: Alq) orbis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), a heterocyclic compound such as3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ), bathophenanthroline (abbreviation: BPhen), orbathocuproine (abbreviation: BCP), a condensed aromatic compound such asCzPA, DNA, t-BuDNA, or DPAnth, an aromatic amine compound such as NPB,or the like can be used.

Alternatively, as the host material, plural kinds of materials can beused. For example, in order to suppress crystallization, a substancesuch as rubrene which suppresses crystallization, may be further added.In addition, NPB, Alq, or the like may be further added in order toefficiently transfer energy to the guest material.

Further, when a plurality of light-emitting layers are provided andemission colors of the layers are made different, light emission of adesired color can be obtained from the light-emitting element as awhole. For example, the emission colors of first and secondlight-emitting layers are complementary in a light-emitting elementhaving the two light-emitting layers, so that the light-emitting elementcan be made to emit white light as a whole. Further, the same applies toa light-emitting element having three or more light-emitting layers.

<Electron-Transport Layer 304>

The electron-transport layer 304 contains a substance with a highelectron-transport property.

The substance with a high electron-transport property is preferably anorganic compound having a property of transporting more electrons thanholes, and is especially preferably a substance with an electronmobility of 10⁻⁶ cm²/Vs or more.

As the substance having a high electron-transport property, for example,a metal complex having a quinoline skeleton or a benzoquinolineskeleton, such as Alq or Balq, or a metal complex having anoxazole-based ligand or a thiazole-based ligand, such asbis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX)₂) orbis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation: Zn(BTZ)₂) canbe used. Alternatively, TAZ, BPhen, BCP, or the like can be used.

<Electron-Injection Layer 305>

The electron-injection layer 305 contains a substance with a highelectron-injection property.

Examples of the substance with a high electron-injection propertyinclude an alkali metal, an alkaline earth metal, or a compound thereof,such as lithium, cesium, calcium, lithium fluoride, cesium fluoride,calcium fluoride, or lithium oxide, can be used. A rare earth metalcompound such as erbium fluoride can also be used. Furtheralternatively, any of the above-described substances that are used toform the electron-transport layer 304 can be used.

<Charge-Generation Region>

The charge-generation region included in the hole-injection layer andthe charge-generation region 308 each contain a substance with a highhole-transport property and an acceptor substance (electron acceptor).Note that the acceptor substance is preferably added so that the massratio of the acceptor substance to the substance with a highhole-transport property is 0.1:1 to 4.0:1.

The charge-generation region is not limited to a structure in which asubstance with a high hole-transport property and an acceptor substanceare contained in the same film, and may have a structure in which alayer containing a substance with a high hole-transport property and alayer containing an acceptor substance are stacked. Note that in thecase of a stacked-layer structure in which the charge-generation regionis provided on the cathode side, the layer containing the substance witha high hole-transport property is in contact with the cathode, and inthe case of a stacked-layer structure in which the charge-generationregion is provided on the anode side, the layer containing the acceptorsubstance is in contact with the anode.

The substance with a high hole-transport property is preferably anorganic compound having a property of transporting more holes thanelectrons, and is especially preferably an organic compound with a holemobility of 10⁻⁶ cm²/Vs or more.

Specifically, it is possible to use any of the substances with a highhole-transport property shown as substances that can be used for thehole-transport layer 302, such as aromatic amine compounds such as NPBand BPAFLP, carbazole derivatives such as CBP, CzPA, and PCzPA, aromatichydrocarbon compounds such as t-BuDNA, DNA, and DPAnth, and highmolecular compounds such as PVK and PVTPA.

Examples of the acceptor substance include organic compounds, such as7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ) and chloranil, oxides of transition metals, and oxides ofmetals that belong to Groups 4 to 8 in the periodic table. Specifically,vanadium oxide, niobium oxide, tantalum oxide, chromium oxide,molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide arepreferable since their electron-accepting property is high. Inparticular, use of molybdenum oxide is preferable because of itsstability in the atmosphere, a low hygroscopic property, and easilyhandling.

<Electron-Injection Buffer Layer 306>

The electron-injection buffer layer 306 contains a substance with a highelectron-injection property. The electron-injection buffer layer 306facilitates electron injection from the charge-generation region 308into the EL layer 203. As the substance with a high electron-injectionproperty, any of the above-described substances can be used.Alternatively, the electron-injection buffer layer 306 may contain anyof the above-described substances with a high electron-transportproperty and donor substances.

<Electron-Relay Layer 307>

The electron-relay layer 307 immediately accepts electrons drawn out bythe acceptor substance in the charge-generation region 308.

The electron-relay layer 307 contains a substance with a highelectron-transport property. As the substance with a highelectron-transport property, a phthalocyanine-based material or a metalcomplex having a metal-oxygen bond and an aromatic ligand is preferablyused.

As the phthalocyanine-based material, specifically, it is possible touse CuPc or vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine(PhO-VOPc).

As the metal complex having a metal-oxygen bond and an aromatic ligand,a metal complex having a metal-oxygen double bond is preferably used. Ametal-oxygen double bond has an acceptor property; thus, electrons cantransfer (be donated and accepted) more easily.

As the metal complex having a metal-oxygen bond and an aromatic ligand,a phthalocyanine-based material is also preferably used.

As the phthalocyanine-based material, a phthalocyanine-based materialhaving a phenoxy group is preferably used. Specifically, aphthalocyanine derivative having a phenoxy group, such as PhO-VOPc, ispreferably used. The phthalocyanine derivative having a phenoxy group issoluble in a solvent; thus, the phthalocyanine derivative has anadvantage of being easily handled during formation of a light-emittingelement and an advantage of facilitating maintenance of an apparatusused for deposition.

The electron-relay layer 307 may further contain any of theabove-described donor substances. When the donor substance is containedin the electron-relay layer 307, electrons can transfer easily and thelight-emitting element can be driven at a lower voltage.

The LUMO levels of the substance with a high electron-transport propertyand the donor substance are preferably −5.0 eV to −3.0 eV, i.e., betweenthe LUMO level of the acceptor substance contained in thecharge-generation region 308 and the LUMO level of the substance with ahigh electron-transport property contained in the electron-transportlayer 304 (or the LUMO level of the EL layer 203 in contact with theelectron-relay layer 307 or with the electron-injection buffer layer306). When a donor substance is contained in the electron-relay layer307, as the substance with a high electron-transport property, asubstance with a LUMO level higher than the acceptor level of theacceptor substance contained in the charge-generation region 308 can beused.

The above-described layers included in the EL layer 203 and theintermediate layer 207 can be formed separately by any of the followingmethods: an evaporation method (including a vacuum evaporation method),a transfer method, a printing method, an inkjet method, a coatingmethod, and the like.

This embodiment can be freely combined with any of the otherembodiments.

Embodiment 4

In this embodiment, examples of electronic devices and lighting devicesto which one embodiment of the present invention is applied aredescribed with reference to FIGS. 5A to 5E and FIGS. 6A and 6B.

By use of a light-emitting element manufactured according to oneembodiment of the present invention, a passive matrix light-emittingdevice or an active matrix light-emitting device in which driving of thelight-emitting element is controlled by a transistor (hereinafterreferred to as a light-emitting device according to one embodiment ofthe present invention) can be manufactured. The light-emitting devicecan be applied to an electronic device, a lighting device, or the like.The light-emitting device used for an electronic device and a lightingdevice of this embodiment has high reliability because a light-emittingelement manufactured according to one embodiment of the presentinvention is included.

Examples of the electronic device using a light-emitting device to whichone embodiment of the present invention is applied is used include:television sets (also called TV or television receivers); monitors forcomputers or the like; cameras such as digital cameras or digital videocameras; digital photo frames; mobile phones (also called cellularphones or portable telephones); portable game machines; portableinformation terminals; audio playback devices; and large game machinessuch as pachinko machines. Specific examples of these electronic devicesand lighting devices are illustrated in FIGS. 5A to 5E and FIGS. 6A and6B.

FIG. 5A illustrates an example of a television device. In a televisiondevice 7100, a display portion 7102 is incorporated in a housing 7101.The display portion 7102 is capable of displaying images. Thelight-emitting device according to one embodiment of the presentinvention can be used for the display portion 7102. In addition, here,the housing 7101 is supported by a stand 7103.

The television device 7100 can be operated by an operation switch of thehousing 7101 or a separate remote controller 7111. With operation keysof the remote controller 7111, channels and volume can be controlled andimages displayed on the display portion 7102 can be controlled. Further,the remote controller 7111 may be provided with a display portion fordisplaying data output from the remote controller 7111.

Note that the television device 7100 is provided with a receiver, amodem, and the like. With the receiver, general television broadcastingcan be received. Furthermore, when the television device 7100 isconnected to a communication network with or without wires via themodem, one-way (from a sender to a receiver) or two-way (between asender and a receiver or between receivers) information communicationcan be performed.

FIG. 5B illustrates an example of a computer. A computer 7200 includes amain body 7201, a housing 7202, a display portion 7203, a keyboard 7204,an external connecting port 7205, a pointing device 7206, and the like.Note that this computer is manufactured using the light-emitting deviceaccording to one embodiment of the present invention for the displayportion 7203.

FIG. 5C illustrates an example of a portable game machine. A portablegame machine 7300 includes two housings, a housing 7301 a and a housing7301 b, which are connected with a joint portion 7302 so that theportable game machine can be opened or folded. A display portion 7303 ais incorporated in the housing 7301 a and a display portion 7303 b isincorporated in the housing 7301 b. In addition, the portable gamemachine illustrated in FIG. 5C includes a speaker portion 7304, arecording medium insertion portion 7305, operation keys 7306, aconnection terminal 7307, a sensor 7308 (a sensor having a function ofmeasuring force, displacement, position, speed, acceleration, angularvelocity, rotational frequency, distance, light, liquid, magnetism,temperature, chemical substance, sound, time, hardness, electric field,current, voltage, electric power, radiation, flow rate, humidity,gradient, vibration, smell, or infrared ray), an LED lamp, a microphone,and the like. It is needless to say that the structure of the portablegame machine is not limited to the above as long as the light-emittingdevice according to one embodiment of the present invention is used forat least either the display portion 7303 a or the display portion 7303b, or both of them. The portable game machine may be provided with otheraccessories as appropriate. The portable game machine in FIG. 5C has afunction of reading a program or data stored in a recording medium todisplay it on the display portion, and a function of sharing informationwith another portable game machine by wireless communication. Theportable game machine illustrated in FIG. 5C can have a variety offunctions without limitation to the above.

FIG. 5D illustrates an example of a mobile phone. A mobile phone 7400 isprovided with a display portion 7402 incorporated in a housing 7401, anoperation button 7403, an external connection port 7404, a speaker 7405,a microphone 7406, and the like. The mobile phone 7400 is manufacturedusing the light-emitting device according to one embodiment of thepresent invention for the display portion 7402.

When the display portion 7402 of the mobile phone 7400 illustrated inFIG. 5D is touched with a finger or the like, data can be input into themobile phone 7400. Further, operations such as making a call andcreating e-mail can be performed by touch on the display portion 7402with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying images. The secondmode is an input mode mainly for inputting data such as text. The thirdmode is a display-and-input mode in which two modes of the display modeand the input mode are combined.

For example, in the case of making a call or composing an e-mail, a textinput mode mainly for inputting text is selected for the display portion7402 so that text displayed on a screen can be input.

When a detection device including a sensor for detecting inclination,such as a gyroscope or an acceleration sensor, is provided inside themobile phone 7400, display on the screen of the display portion 7402 canbe automatically changed by determining the orientation of the mobilephone 7400 (whether the cellular phone is placed horizontally orvertically for a landscape mode or a portrait mode).

The screen modes are switched by touching the display portion 7402 oroperating the operation button 7403 of the housing 7401. Alternatively,the screen modes can be switched depending on kinds of images displayedon the display portion 7402. For example, when a signal of an imagedisplayed on the display portion is a signal of moving image data, thescreen mode is switched to the display mode. When the signal is a signalof text data, the screen mode is switched to the input mode.

Moreover, in the input mode, when input by touching the display portion7402 is not performed within a specified period while a signal detectedby an optical sensor in the display portion 7402 is detected, the screenmode may be controlled so as to be switched from the input mode to thedisplay mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken by touchon the display portion 7402 with the palm or the finger, wherebypersonal authentication can be performed. Further, by providing abacklight or a sensing light source which emits a near-infrared light inthe display portion, an image of a finger vein, a palm vein, or the likecan be taken.

FIG. 5E illustrates an example of a fordable tablet terminal (in an openstate). A tablet terminal 7500 includes a housing 7501 a, a housing 7501b, a display portion 7502 a, and a display portion 7502 b. The housing7501 a and the housing 7501 b are connected by a hinge 7503 and can beopened and closed along the hinge 7503. The housing 7501 a includes apower switch 7504, operation keys 7505, a speaker 7506, and the like.Note that the tablet terminal 7500 is manufactured using thelight-emitting device according to one embodiment of the presentinvention for either the display portion 7502 a or the display portion7502 b, or both of them.

Part of the display portion 7502 a or the display portion 7502 b, inwhich data can be input by touching displayed operation keys can be usedas a touch panel region. For example, the entire area of the displayportion 7502 a can display keyboard buttons and serve as a touch panelwhile the display portion 7502 b can be used as a display screen.

FIG. 6A illustrates a desk lamp including a lighting portion 7601, ashade 7602, an adjustable arm 7603, a support 7604, a base 7605, and apower switch 7606. The desk lamp is manufactured using thelight-emitting device according to one embodiment of the presentinvention for the lighting portion 7601. Note that a lamp includes aceiling light, a wall light, and the like in its category.

FIG. 6B illustrates an example in which the light-emitting deviceaccording to one embodiment of the present invention is used for anindoor lighting device 7701. Since the light-emitting device accordingto one embodiment of the present invention can have a larger area, itcan be used as a large-area lighting device. In addition, thelight-emitting device can be used as a roll-type lighting device 7702.As illustrated in FIG. 6B, a desk lamp 7703 described with reference toFIG. 6A may be used in a room provided with the indoor lighting device7701.

This embodiment can be freely combined with any of the otherembodiments.

EXAMPLE 1

In this example, a light-emitting element manufactured by a method formanufacturing a light-emitting element according to one embodiment ofthe present invention is described with reference to FIG. 7A. Chemicalformulae of materials used in this example are shown below.

A light-emitting element 1 and a comparative light-emitting element 2which are described in this example are provided over a substrate 1100and have a structure in which an EL layer 1102 is provided between afirst electrode 1101 and a second electrode 1103, and materials andthicknesses of layers included in the EL layers 1102 are the same. Thelight-emitting element 1 and the comparative light-emitting element 2are different in a method for forming a lithium film included in anintermediate layer 505. First, common points of the two light-emittingelements about the manufacturing methods are described below, and then,different points (that is, the methods for manufacturing the lithiumfilms) of the two elements are described.

(Method for Manufacturing Light-Emitting Element 1 and ComparativeLight-Emitting Element 2)

First, a film of indium tin oxide containing silicon oxide (ITSO) wasdeposited over the substrate 1100 which was a glass substrate by asputtering method to form the first electrode 1101. The thickness was110 nm and the electrode area was 2 mm×2 mm.

Next, as pretreatment, after a substrate surface was cleaned, drytreatment was performed in a nitrogen atmosphere at 200° C. for 1 hour.

After that, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 10⁻⁴ Pa,and subjected to vacuum baking at 150° C. for 1 hour in a heatingchamber of the vacuum evaporation apparatus, and then, the substrate1100 was cooled down to room temperature.

Next, the substrate 1100 was fixed to a substrate holder in the vacuumevaporation apparatus so that a surface of the substrate 1100 on whichthe first electrode 1101 was formed faced downward. The pressure in thevacuum evaporation apparatus was reduced to about 10⁻⁴ Pa. Then, by anevaporation method using resistance heating,9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:PCzPA) and molybdenum(VI) oxide were co-deposited to form a firsthole-injection layer 501 a. The thickness of the first hole-injectionlayer 501 a was set to 37 nm, and the mass ratio of PCzPA to molybdenumoxide was adjusted to 2:1 (=PCzPA: molybdenum oxide). Note that theco-deposition method refers to a deposition method in which depositionis carried out using a plurality of evaporation sources at the same timein one treatment chamber.

Next, PCzPA was deposited to a thickness of 30 nm over the firsthole-injection layer 501 a, so that a first hole-transport layer 502 awas formed.

Then, 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:CzPA) andN,N′-bis(3-methylphenyl)-N,N-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn) were co-deposited over the firsthole-transport layer 502 a, so that a first light-emitting layer 503 awas formed. The thickness of the first light-emitting layer 503 a wasset to 30 nm, and the mass ratio of CzPA to 1,6mMemFLPAPrn was adjustedto 2:0.05 (=CzPA: 1,6mMemFLPAPrn).

Next, over the first light-emitting layer 503 a, CzPA was deposited to athickness of 5 nm and then bathophenanthroline (abbreviation: BPhen) wasdeposited to a thickness of 15 nm, so that a first electron-transportlayer 504 a was formed.

Next, over the first electron-transport layer 504 a, lithium (Li) wasdeposited to a thickness of 0.15 nm and then copper phthalocyanine(abbreviation: CuPc) was deposited to a thickness of 2 nm, so that theintermediate layer 505 was formed. As described above, thelight-emitting element 1 and the comparative light-emitting element 2are different in the method for forming a lithium film included in theintermediate layer 505. The details will be described later.

Next, over the intermediate layer 505,4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylainine (abbreviation: BPAFLP)and molybdenum(VI) oxide were co-deposited, so that a secondhole-injection layer 501 b was formed. The thickness of the secondhole-injection layer 501 b was 37 nm, and the mass ratio of BPAFLP tomolybdenum oxide was adjusted to 2:1 (=BPAFLP: molybdenum oxide).

Next, BPAFLP was deposited to a thickness of 20 nm over the secondhole-injection layer 501 b, so that a second hole-transport layer 502 bwas formed.

Next, 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTPDBq-II),4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP), and(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]) were co-deposited to form a secondlight-emitting layer 503 b over the second hole-transport layer 502 b.Here, the mass ratio of 2mDBTPDBq-II to PCBA1BP and [Ir(tBuppm)₂(acac)]was adjusted to 1.2:0.8:0.12 (=2mDBTPDBq-II: PCBA1BP:[Ir(tBuppm)₂(acac)]). In addition, the thickness of the secondlight-emitting layer 503 b was set to 10 nm.

Further, 2mDB TPDB q-II, PCBA1BP, and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]) were co-deposited, whereby a thirdlight-emitting layer 503 c was formed over the second light-emittinglayer 503 b. Here, the mass ratio of 2mDBTPDBq-II to PCBA1BP and[Ir(dppm)₂(acac)] was adjusted to 1.6:0.4:0.12 (=2mDBTPDBq-II: PCBA1BP:[Ir(dppm)₂(acac)]). The thickness of the third light-emitting layer 503c was set to 30 nm.

Next, over the third light-emitting layer 503 c, 2mDBTPDBq-II wasdeposited to a thickness of 15 nm and then BPhen was deposited to athickness of 15 nm, so that a second electron-transport layer 504 b wasformed.

Further, lithium fluoride (LiF) was deposited to a thickness of 1 nmover the second electron-transport layer 504 b, whereby anelectron-injection layer 506 was formed.

Lastly, aluminum was deposited to a thickness of 200 nm as the secondelectrode 1103 functioning as a cathode. Thus, the light-emittingelement of this example was manufactured.

Note that in the above deposition process, deposition was all performedby a resistance heating method.

In a glove box containing a nitrogen atmosphere, the light-emittingelements of this example were sealed with a glass substrate so as not tobe exposed to the atmosphere. Then, operation characteristics of theselight-emitting elements were measured. Note that the measurement wascarried out at room temperature (in an atmosphere kept at 25° C.).

Here, the method for forming a lithium film included in the intermediatelayer 505, which is a difference between the light-emitting element 1and the comparative light-emitting element 2, is described withreference to FIGS. 8A and 8B, FIGS. 9A and 9B, and FIG. 10.

FIGS. 8A and 8B show results of the partial pressure of water (¹⁸H₂O) ina deposition chamber in which a lithium film included in thelight-emitting element of this example is deposited, which is measuredwith a quadrupole mass spectrometer. Further, FIGS. 9A and 9B showresults of the partial pressure of oxygen atoms (¹⁶O) in the depositionchamber, which is measured with a quadrupole mass spectrometer. FIG. 8Aand FIG. 9A each show measurement results for 3.5 hours from the startof the measurement with the quadrupole mass spectrometer, and FIG. 8Band FIG. 9B each show measurement results in the range from 2.20 hoursto 3.30 hours including a period during which the lithium films of thelight-emitting element 1 and the comparative light-emitting element 2were formed.

First, after the temperature of a heating mechanism (here, a heater)included in a deposition material holding portion was increased to 320°C., the temperature was kept at about 320° C. and moisture in adeposition material (lithium) was removed.

Next, about 1.95 hours later, the temperature of the heating mechanismwas further increased to higher than or equal to a temperature at whichlithium is vaporized.

Then, in the range from 2.22 hours to 2.37 hours (period A shown in eachof FIG. 8B and FIG. 9B), the lithium film of the comparativelight-emitting element 2 was formed. The average partial pressure ofwater in the period A was 1.1×10⁻⁵ Pa, and the average partial pressureof oxygen atoms in the period A was 2.38×10⁻⁶ Pa.

After that, a substrate placed in the deposition chamber was switchedfrom a supporting substrate of the comparative light-emitting element 2to a supporting substrate of the light-emitting element 1. Then, it wasconfirmed that the partial pressure of water became smaller than theaverage partial pressure of water in the period A, and the lithium filmof the light-emitting element 1 was formed in the range from 3.13 hoursto 3.27 hours (period B shown in each of FIG. 8B and FIG. 9B). Note thatthe average partial pressure of water in the period B was 7.8×10⁻⁶ Pa,and the average partial pressure of oxygen atoms was 1.23×10⁻⁶ Pa. Asdescribed above, the lithium film of the light-emitting element 1 wasformed in the deposition chamber in which the partial pressure of waterand the partial pressure of oxygen atoms were smaller than those in thecomparative light-emitting element 2.

FIG. 10 shows the ratio (16/18) of the partial pressure of oxygen atoms(¹⁶O) to the partial pressure of water (¹⁸H₂O) shown in FIGS. 8A and 8Band FIGS. 9A and 9B. For comparison, FIG. 10 also shows the ratio(17/18) of the partial pressure of a hydroxide ion having a molecularweight of 17 (¹⁷OH⁻) to the partial pressure of water (¹⁸H₂O).

In FIG. 10, the ratio of the partial pressure of a hydroxide ion havinga mass number of 17 with respect to the partial pressure of water havinga mass number of 18 does not change depending on the time. On the otherhand, the ratio of the partial pressure of oxygen atoms having a massnumber of 16 with respect to the partial pressure of water having a massnumber of 18 largely changes depending on the time. This indicates thatthe partial pressure of a hydroxide ion having a mass number of 17 isaffected by water in the deposition material or the amount of moisturein the deposition chamber. On the other hand, it is indicated that thepartial pressure of oxygen atoms having a mass number of 16 is affectedby not only the amount of moisture but also the amount of oxygencontained in the deposition material. It can be said from these resultsthat in one embodiment of the present invention, deposition ispreferably performed while the partial pressure of oxygen atoms (¹⁶O) ina deposition chamber is measured with a quadrupole mass spectrometer.

Table 1 shows element structures of the light-emitting element 1 and thecomparative light-emitting element 2 obtained as described above.

TABLE 1 First electrode ITSO 110 nm First hole- First hole- transportFist electron- Intermediate injection layer layer First light-emittinglayer transport layer layer PCzPA:MoOx PCzPA CzPA:1,6mMeinFLPAPm CzPABPhen Li CuPc (=2:1) 30 nm (=2:0.05) 5 nm 15 nm 0.15 nm 2 nm 37 nm 30 nmSecond hole- Second hole- transport injection layer layer Secondlight-emitting layer Third light-emitting layer BPAFLP:MoOx BPAFLP2mDBTPDBq-II:PCBA1BP: 2mDBTPDBq-II:PCBA1BP: (=2:1) 20 nm[Ir(tBuppm)2(acac)] [Ir(dppm)2(acac)] 37 nm (=1.2:0.8:0.12) 10 nm(=1.6:0.4:0.12) 30 nm Electron- Second electron-transport injectionSecond layer layer electrode 2mDBTPDBq-II BPhen LiF Al 15 nm 15 nm 1 nm200 nm

FIG. 11A shows luminance-current efficiency characteristics of thelight-emitting element 1 and the comparative light-emitting element 2.In FIG. 11A, the horizontal axis represents luminance (cd/m²), and thevertical axis represents current efficiency (cd/A). FIG. 11B showsvoltage-current characteristics. In FIG. 11B, the horizontal axisrepresents voltage (V), and the vertical axis represents current (mA).FIG. 12A shows emission spectra of the light-emitting elements of thisexample which were obtained by applying a current of 0.1 mA. In FIG.12A, the horizontal axis represents wavelength (ma), and the verticalaxis represents emission intensity (arbitrary unit).

Further, Table 2 shows the voltage (V), current density (mA/cm²), CIEchromaticity coordinates (x, y), luminance (cd/m²), current efficiency(cd/A), and power efficiency (lm/W) of each light-emitting element at aluminance of around 1000 cd/m².

TABLE 2 Current Current Power Voltage density Chromaticity Luminanceefficiency efficiency (V) (mA/cm²) (x, y) (cd/m²) (cd/A) (lm/W)Light-emitting 5.9 1.38 (0.40, 0.39)  900 66 35 element 1 Comparativelight-emitting 6.0 1.66 (0.39, 0.40) 1100 65 34 element 2

As shown in FIGS. 11A and 11B, luminance-current efficiencycharacteristics and voltage-current characteristics do not differbetween the light-emitting element 1 and the comparative light-emittingelement 2. Further, as shown in FIG. 12A, the light-emitting element 1and the comparative light-emitting element 2 show almost similaremission spectra.

Next, the light-emitting element 1 and the comparative light-emittingelement 2 were subjected to reliability tests. Results of thereliability tests are shown in FIG. 12B. In FIG. 12B, the vertical axisrepresents normalized luminance (%) with an initial luminance of 100%,and the horizontal axis represents driving time (h) of the elements. Inthe reliability tests, the light-emitting elements of this example weredriven at room temperature under the conditions where the initialluminance was set to 5000 cd/m² and the current density was constant.FIG. 12B shows that the light-emitting element 1 kept 76% of the initialluminance after driving for 2300 hours and the comparativelight-emitting element 2 kept 72% of the initial luminance after drivingfor 1500 hours. These results of the reliability tests revealed that thelight-emitting element 1 has a longer lifetime than the comparativelight-emitting element 2.

The manufacturing process of the light-emitting element 1 and that ofthe comparative light-emitting element 2 were different in anenvironment of the deposition chamber (the partial pressure of water andthe partial pressure of oxygen atoms) at formation of the lithium films.In addition, in the comparative light-emitting element 2, there was noperiod during which the deposition material was heated and vaporizedbefore a period during which the lithium film was formed (period A). Onthe other hand, in the light-emitting element 1 to which one embodimentof the present invention was applied, there was a period during whichthe deposition material was heated and vaporized (period A) before aperiod during which the lithium film was formed (period B). In addition,at the start of the period B, the partial pressure of water in thedeposition chamber was lower than the average partial pressure of waterin the period A. Further, at the start of the period B, the partialpressure of oxygen atoms in the deposition chamber was lower than theaverage partial pressure of oxygen atoms in the period A.

The difference of results in the reliability tests between thelight-emitting element 1 and the comparative light-emitting element 2 isthought to be due to the difference of conditions at formation of theabove lithium films. This example shows that a light-emitting elementhaving a long lifetime can be manufactured by application of oneembodiment of the present invention.

EXAMPLE 2

In this example, a light-emitting element manufactured by a method formanufacturing a light-emitting element according to one embodiment ofthe present invention is described with reference to FIG. 7B. Materialsused in this example are the same as those used in Example 1, and theirchemical formulae are omitted here.

A light-emitting element 3 and a comparative light-emitting element 4which are described in this example are provided over the substrate 1100and have a structure in which the EL layer 1102 is provided between thefirst electrode 1101 and the second electrode 1103, and materials andthicknesses of layers included in the EL layers 1102 are the same.

A pair of electrodes included in each of the light-emitting element 3and the comparative light-emitting element 4 is manufactured underconditions (a material, a thickness, or the like) similar to those inExample 1. Further, the EL layer 1102 included in each of thelight-emitting element 3 and the comparative light-emitting element 4includes a hole-injection layer 501, a hole-transport layer 502, alight-emitting layer 503, an electron-transport layer 504, and theelectron-injection layer 506.

The hole-injection layer 501 is formed using a material similar to thatof the first hole-injection layer 501 a in Example 1 and has a thicknessof 50 nm. The light-emitting element 3 and the comparativelight-emitting element 4 are different in a method for forming thehole-injection layer 501.

The hole-transport layer 502, the light-emitting layer 503, theelectron-transport layer 504, and the electron-injection layer 506 areformed under conditions (materials, thicknesses, or the like) similar tothose of the first hole-transport layer 502 a, the first light-emittinglayer 503 a, the first electron-transport layer 504 a, and theelectron-injection layer 506 in Example 1, respectively.

The method for forming the hole-injection layer 501, which is adifference between the light-emitting element 3 and the comparativelight-emitting element 4, is described below with reference to FIG. 13and FIGS. 14A and 14B.

FIG. 13 and FIGS. 14A and 14B show results of the partial pressure ofwater (¹⁸H₂O) in a deposition chamber in which the hole-injection layer501 included in the light-emitting element of this example is deposited,which was measured with a quadrupole mass spectrometer. FIG. 13 showsmeasurement results for 3.0 hours from the start of the measurement withthe quadrupole mass spectrometer, FIG. 14A shows measurement results inthe range from 0.70 hours to 0.90 hours including a period during whichthe hole-injection layer 501 of the comparative light-emitting element 4was formed, and FIG. 14B shows measurement results in the range from2.75 hours to 2.95 hours including a period during which thehole-injection layer 501 of the light-emitting element 3 was formed.

First, the temperature of a heating mechanism (here, a heater) includedin a deposition material holding portion was increased to 150° C., andthen further increased to higher than or equal to a temperature at whichPCzPA and molybdenum oxide were vaporized.

Then, in the range from 0.78 hours to 0.83 hours (period C in FIG. 14A),a hole-injection layer of the comparative light-emitting element 4 wasformed. The average partial pressure of water in the period C was1.19×10⁻⁴ Pa.

After that, a substrate placed in the deposition chamber was switchedfrom a supporting substrate of the comparative light-emitting element 4to a supporting substrate of the light-emitting element 3. Then, it wasconfirmed that the partial pressure of water became smaller than theaverage partial pressure of water in the period C, and thehole-injection layer of the light-emitting element 3 was formed in therange from 2.83 hours to 2.88 hours (period D shown in FIG. 14B). Notethat the average partial pressure of water in the period D was 9.18×10⁻⁵Pa. As described above, the hole-injection layer of the light-emittingelement 3 was formed in the deposition chamber in which the partialpressure of water was smaller than that in the comparativelight-emitting element 4.

Table 3 shows element structures of the light-emitting element 3 and thecomparative light-emitting element 4 obtained as described above.

TABLE 3 Hole- Electron- Electron- First Hole-injection transporttransport injection Second electrode layer layer Light-emitting layerlayer layer electrode ITSO PCzPA:MoOx PCzPA CzPA:1,6mMemFLPAPm CzPABPhen LiF Al 110 nm (=2:1) 30 nm (=2:0.05) 5 nm 15 nm 1 nm 200 nm 50 nm30 nm

FIG. 15A shows luminance-current efficiency characteristics of thelight-emitting element 3 and the comparative light-emitting element 4.In FIG. 15A, the horizontal axis represents luminance (cd/m²), and thevertical axis represents current efficiency (cd/A). FIG. 15B showsvoltage-current characteristics. In FIG. 15B, the horizontal axisrepresents voltage (V), and the vertical axis represents current (mA).FIG. 16 shows emission spectra of the light-emitting elements of thisexample which were obtained by applying a current of 0.1 mA. In FIG. 16,the horizontal axis represents wavelength (nm), and the vertical axisrepresents emission intensity (arbitrary unit).

Further, Table 4 shows the voltage (V), current density (mA/cm²), CIEchromaticity coordinates (x, y), luminance (cd/m²), current efficiency(cd/A), and power efficiency (lm/W) of each light-emitting element at aluminance of around 1000 cd/m².

TABLE 4 Current Current Power Voltage density Chromaticity Luminanceefficiency efficiency (V) (mA/cm²) (x, y) (cd/m²) (cd/A) (lm/W)Light-emitting 3.1 13.7 (0.14, 0.16) 1100 7.7 7.8 element 3 Comparativelight-emitting 3.1 11.9 (0.14, 0.16)  900 7.3 7.4 element 4

As shown in FIGS. 15A and 15B, luminance-current efficiencycharacteristics and voltage-current characteristics do not differbetween the light-emitting element 3 and the comparative light-emittingelement 4. Further, as shown in FIG. 16, the light-emitting element 3and the comparative light-emitting element 4 show almost similaremission spectra.

Next, the light-emitting element 3 and the comparative light-emittingelement 4 were subjected to reliability tests. Results of thereliability tests are shown in FIG. 17. In FIG. 17, the vertical axisrepresents normalized luminance (%) with an initial luminance of 100%,and the horizontal axis represents driving time (h) of the elements. Inthe reliability tests, the light-emitting elements of this example weredriven at room temperature under the conditions where the initialluminance was set to 1000 cd/m² and the current density was constant.FIG. 17 shows that the comparative light-emitting element 4 kept lowerthan 70% of the initial luminance after driving for 570 hours. On theother hand, the light-emitting element 3 kept 86% of the initialluminance after the driving for 1800 hours. These results of thereliability tests revealed that the light-emitting element 3 has alonger lifetime than the comparative light-emitting element 4.

The manufacturing process of the light-emitting element 3 and that ofthe comparative light-emitting element 4 were different in anenvironment of the deposition chamber (the partial pressure of water) atformation of the hole-injection layer. In addition, in the comparativelight-emitting element 4, there was no period during which thedeposition material was heated and vaporized before a period duringwhich the hole-injection layer was formed (period C). On the other hand,in the light-emitting element 3 to which one embodiment of the presentinvention was applied, there was a period during which the depositionmaterial was heated and vaporized (period C) before a period duringwhich the hole-injection layer was formed (period D). In addition, atthe start of the period D, the partial pressure of water in thedeposition chamber was lower than the average partial pressure of waterin the period C.

The difference of results in the reliability tests between thelight-emitting element 3 and the comparative light-emitting element 4 isthought to be due to the difference of conditions at formation of theabove hole-injection layers. This example shows that a light-emittingelement having a long lifetime can be manufactured by application of oneembodiment of the present invention.

EXAMPLE 3

In this example, a light-emitting element manufactured by a method formanufacturing a light-emitting element according to one embodiment ofthe present invention is described with reference to FIG. 7B. Materialsused in this example are the same as those used in Example 1, and theirchemical formulae are omitted here.

A light-emitting element 5 and a comparative light-emitting element 6which are described in this example are provided over the substrate 1100and have a structure in which the EL layer 1102 is provided between thefirst electrode 1101 and the second electrode 1103, and materials andthicknesses of layers included in the EL layers 1102 are the same.

A pair of electrodes included in each of the light-emitting element 5and the comparative light-emitting element 6 is manufactured underconditions (a material, a thickness, or the like) similar to those inExample 1. Further, the EL layer 1102 included in each of thelight-emitting element 5 and the comparative light-emitting element 6includes the hole-injection layer 501, the hole-transport layer 502, thelight-emitting layer 503, the electron-transport layer 504, and theelectron-injection layer 506.

The hole-injection layer 501, the hole-transport layer 502, theelectron-transport layer 504, and the electron-injection layer 506 areformed under conditions (materials, thicknesses, or the like) similar tothose of the first hole-injection layer 501 a, the first hole-transportlayer 502 a, the first electron-transport layer 504 a, and theelectron-injection layer 506 in Example 1, respectively.

The light-emitting layer 503 is formed using a material and a thicknesssimilar to those of the first light-emitting layer 503 a in Example 1.The light-emitting element 5 and the comparative light-emitting element6 are different in a method for forming the light-emitting layer 503.

The method for forming the light-emitting layer 503, which is adifference between the light-emitting element 5 and the comparativelight-emitting element 6, is described below with reference to FIG. 18and FIGS. 19A and 19B.

FIG. 18 and FIGS. 19A and 19B show results of the partial pressure ofwater (¹⁸H₂O) in a deposition chamber in which the light-emitting layer503 included in the light-emitting element of this example is deposited,which was measured with a quadrupole mass spectrometer. FIG. 18 showsmeasurement results for 2.3 hours from the start of the measurement withthe quadrupole mass spectrometer, FIG. 19A shows measurement results inthe range from 0.50 hours to 0.70 hours including a period during whichthe light-emitting layer 503 of the comparative light-emitting element 6was formed, and FIG. 19B shows measurement results in the range from2.10 hours to 2.30 hours including a period during which thelight-emitting layer 503 of the light-emitting element 5 was formed.

First, the temperature of a heating mechanism (here, a heater) includedin a deposition material holding portion was increased to 150° C., keptat around 150° C., and then further increased to higher than or equal toa temperature at which CzPA and 1,6mMemFLPAPrn were vaporized.

Then, in the range from 0.55 hours to 0.62 hours (period E in FIG. 19A),a light-emitting layer of the comparative light-emitting element 6 wasformed. The average partial pressure of water in the period E was1.70×10⁻⁵ Pa.

After that, a substrate placed in the deposition chamber was switchedfrom a supporting substrate of the comparative light-emitting element 6to a supporting substrate of the light-emitting element 5. Then, it wasconfirmed that the partial pressure of water became smaller than theaverage partial pressure of water in the period E, and thelight-emitting layer of the light-emitting element 5 was formed in therange from 2.15 hours to 2.22 hours (period F shown in FIG. 19B). Notethat the average partial pressure of water in the period F was 9.88×10⁻⁶Pa. As described above, the light-emitting layer of the light-emittingelement 5 was formed in the deposition chamber in which the partialpressure of water was smaller than that of the comparativelight-emitting element 6.

Table 5 shows element structures of the light-emitting element 5 and thecomparative light-emitting element 6 obtained as described above.

TABLE 5 Hole- Electron- Electron- First Hole-injection transporttransport injection Second electrode layer layer Light-emitting layerlayer layer electrode ITSO PCzPA:MoOx 30 nm CzPA:1,6mMemFLPAPm CzPABPhen LiF Al 110 nm (=2:1) (=2:0.05) 5 nm 15 nm 1 nm 200 nm 37 nm 30 nm

FIG. 20A shows luminance-current efficiency characteristics of thelight-emitting element 5 and the comparative light-emitting element 6.In FIG. 20A, the horizontal axis represents luminance (cd/m²), and thevertical axis represents current efficiency (cd/A). FIG. 20B showsvoltage-current characteristics. In FIG. 20B, the horizontal axisrepresents voltage (V), and the vertical axis represents current (mA).FIG. 21 shows emission spectra of the light-emitting elements of thisexample which were obtained by applying a current of 0.1 mA. In FIG. 21,the horizontal axis represents wavelength (nm), and the vertical axisrepresents emission intensity (arbitrary unit).

Further, Table 6 shows the voltage (V), current density (mA/cm²), CIEchromaticity coordinates (x, y), luminance (cd/m²), current efficiency(cd/A), and power efficiency (lm/W) of each light-emitting element at aluminance of around 1000 cd/m².

TABLE 6 Current Current Power Voltage density Chromaticity Luminanceefficiency efficiency (V) (mA/cm²) (x, y) (cd/m²) (cd/A) (lm/W)Light-emitting 3.1 18.4 (0.14, 0.16) 1400 7.6 7.7 element 5 Comparativelight-emitting 3.1 14.6 (0.14, 0.15) 1100 7.6 7.7 element 6

As shown in FIGS. 20A and 20B, luminance-current efficiencycharacteristics and voltage-current characteristics do not differbetween the light-emitting element 5 and the comparative light-emittingelement 6. Further, as shown in FIG. 21, the light-emitting element 5and the comparative light-emitting element 6 show almost similaremission spectra.

Next, the light-emitting element 5 and the comparative light-emittingelement 6 were subjected to reliability tests. Results of thereliability tests are shown in FIG. 22. In FIG. 22, the vertical axisrepresents normalized luminance (%) with an initial luminance of 100%,and the horizontal axis represents driving time (h) of the elements. Inthe reliability tests, the light-emitting elements of this example weredriven at room temperature under the conditions where the initialluminance was set to 1000 cd/m² and the current density was constant.FIG. 22 shows that the comparative light-emitting element 6 kept 76% ofthe initial luminance after driving for 2500 hours. On the other hand,the light-emitting element 5 kept 79% of the initial luminance after thedriving for 2500 hours. These results of the reliability tests revealedthat the light-emitting element 5 has a longer lifetime than thecomparative light-emitting element 6.

The manufacturing process of the light-emitting element 5 and that ofthe comparative light-emitting element 6 were different in anenvironment of the deposition chamber (the partial pressure of water) atformation of the light-emitting layer. In addition, in the comparativelight-emitting element 6, there was no period during which thedeposition material was heated and vaporized before a period duringwhich the light-emitting layer was formed (period E). On the other hand,in the light-emitting element 5 to which one embodiment of the presentinvention was applied, there was a period during which the depositionmaterial was heated and vaporized (period E) before a period duringwhich the light-emitting layer was formed (period F). In addition, atthe start of the period F, the partial pressure of water in thedeposition chamber was lower than the average partial pressure of waterin the period E.

The difference of results in the reliability tests between thelight-emitting element 5 and the comparative light-emitting element 6 isthought to be due to the difference of conditions at formation of theabove light-emitting layers. This example shows that a light-emittingelement having a long lifetime can be manufactured by application of oneembodiment of the present invention.

EXAMPLE 4

In this example, a light-emitting element manufactured by a method formanufacturing a light-emitting element according to one embodiment ofthe present invention is described with reference to FIG. 7B. Materialsused in this example are the same as those used in Example 1, and theirchemical formulae are omitted here.

A light-emitting element 7 and a comparative light-emitting element 8which are described in this example are provided over the substrate 1100and have a structure in which the EL layer 1102 is provided between thefirst electrode 1101 and the second electrode 1103, and materials andthicknesses of layers included in the EL layers 1102 are the same.

A pair of electrodes included in each of the light-emitting element 7and the comparative light-emitting element 8 is manufactured underconditions (a material, a thickness, or the like) similar to those inExample 1. Further, the EL layer 1102 included in each of thelight-emitting element 7 and the comparative light-emitting element 8includes the hole-injection layer 501, the hole-transport layer 502, thelight-emitting layer 503, the electron-transport layer 504, and theelectron-injection layer 506.

The hole-injection layer 501, the hole-transport layer 502, theelectron-transport layer 504, and the electron-injection layer 506 areformed under conditions (materials, thicknesses, or the like) similar tothe second hole-injection layer 501 b, the second hole-transport layer502 b, the second electron-transport layer 504 b, and theelectron-injection layer 506 in Example 1, respectively. The thicknessof the hole-injection layer 501 was set to 50 nm.

The light-emitting layer 503 is formed using a material similar to thatof the third light-emitting layer 503 c in Example 1 and has a thicknessof 40 nm. The light-emitting element 7 and the comparativelight-emitting element 8 are different in a method for forming thelight-emitting layer 503.

The method for forming the light-emitting layer 503, which is adifference between the light-emitting element 7 and the comparativelight-emitting element 8, is described below with reference to FIG. 23and FIGS. 24A and 24B.

FIG. 23 and FIGS. 24A and 24B show results of the partial pressure ofwater (¹⁸H₂O) in a deposition chamber in which the light-emitting layer503 included in the light-emitting element of this example is deposited,which was measured with a quadrupole mass spectrometer. FIG. 23 showsmeasurement results for 2.7 hours from the start of the measurement withthe quadrupole mass spectrometer, FIG. 24A shows measurement results inthe range from 0.65 hours to 0.85 hours including a period during whichthe light-emitting layer 503 of the comparative light-emitting element 8was formed, and FIG. 24B shows measurement results in the range from2.50 hours to 2.70 hours including a period during which thelight-emitting layer 503 of the light-emitting element 7 was formed.

First, the temperature of a heating mechanism (here, a heater) includedin a deposition material holding portion was increased to 150° C., keptat around 150° C., and then further increased to higher than or equal toa temperature at which 2mDBTPDBq-II, PCBA1BP, and [Ir(dppm)₂(acac)] werevaporized.

Then, in the range from 0.70 hours to 0.80 hours (period G in FIG. 24A),a light-emitting layer of the comparative light-emitting element 8 wasformed. The average partial pressure of water in the period G was1.80×10⁻⁵ Pa.

After that, a substrate placed in the deposition chamber was switchedfrom a supporting substrate of the comparative light-emitting element 8to a supporting substrate of the light-emitting element 7. Then, it wasconfirmed that the partial pressure of water became smaller than theaverage partial pressure of water in the period G, and thelight-emitting layer of the light-emitting element 7 was formed in therange from 2.51 hours to 2.62 hours (period H shown in FIG. 24B). Notethat the average partial pressure of water in the period H was 1.24×10⁻⁵Pa. As described above, the light-emitting layer of the light-emittingelement 7 was formed in the deposition chamber in which the partialpressure of water was smaller than that in the comparativelight-emitting element 8.

Table 7 shows element structures of the light-emitting element 7 and thecomparative light-emitting element 8 obtained as described above.

TABLE 7 Hole- Electron- First Hole-injection transportElectron-transport injection Second electrode layer layer Light-emittinglayer layer layer electrode ITSO BPAFLP:MoOx BPAFLP2mDBTPDBq-II:PCBA1BP:[Ir(dppm)₂(acac)] 2mDBTPDBq-II BPhen LiF Al 110 nm(=2:1) 20 nm (=1.6:0.4:0.12) 15 nm 15 nm 1 nm 200 mn 50 nm 40 nm

FIG. 25A shows luminance-current efficiency characteristics of thelight-emitting element 7 and the comparative light-emitting element 8.In FIG. 25A, the horizontal axis represents luminance (cd/m²), and thevertical axis represents current efficiency (cd/A). FIG. 25B showsvoltage-current characteristics. In FIG. 25B, the horizontal axisrepresents voltage (V), and the vertical axis represents current (mA).FIG. 26 shows emission spectra of the light-emitting elements of thisexample which were obtained by applying a current of 0.1 mA. In FIG. 26,the horizontal axis represents wavelength (nm), and the vertical axisrepresents emission intensity (arbitrary unit).

Further, Table 8 shows the voltage (V), current density (mA/cm²), CIEchromaticity coordinates (x, y), luminance (cd/m²), current efficiency(cd/A), and power efficiency (lm/W) of each light-emitting element at aluminance of around 1000 cd/m².

TABLE 8 Current Current Power Voltage density Chromaticity Luminanceefficiency efficiency (V) (mA/cm²) (x, y) (cd/m²) (cd/A) (lm/W)Light-emitting 2.9 1.1 (0.56, 0.44)  800 77 84 element 7 Comparativelight-emitting 3.0 1.5 (0.56, 0.44) 1100 76 80 element 8

As shown in FIGS. 25A and 25B, luminance-current efficiencycharacteristics and voltage-current characteristics do not differbetween the light-emitting element 7 and the comparative light-emittingelement 8. Further, as shown in FIG. 26, the light-emitting element 7and the comparative light-emitting element 8 show almost similaremission spectra.

Next, the light-emitting element 7 and the comparative light-emittingelement 8 were subjected to reliability tests. Results of thereliability tests are shown in FIG. 27. In FIG. 27, the vertical axisrepresents normalized luminance (%) with an initial luminance of 100%,and the horizontal axis represents driving time (h) of the elements. Inthe reliability tests, the light-emitting elements of this example weredriven at room temperature under the conditions where the initialluminance was set to 5000 cd/m² and the current density was constant.FIG. 27 shows that the comparative light-emitting element 8 kept 77% ofthe initial luminance after driving for 2000 hours. On the other hand,the light-emitting element 7 kept 81% of the initial luminance after thedriving for 2400 hours. These results of the reliability tests revealedthat the light-emitting element 7 has a longer lifetime than thecomparative light-emitting element 8.

The manufacturing process of the light-emitting element 7 and that ofthe comparative light-emitting element 8 were different in anenvironment of the deposition chamber (the partial pressure of water) atformation of the light-emitting layer. In addition, in the comparativelight-emitting element 8, there was no period during which thedeposition material was heated and vaporized before a period duringwhich the light-emitting layer was formed (period G). On the other hand,in the light-emitting element 7 to which one embodiment of the presentinvention was applied, there was a period during which the depositionmaterial was heated and vaporized (period G) before a period duringwhich the light-emitting layer was formed (period H). In addition, atthe start of the period H, the partial pressure of water in thedeposition chamber was lower than the average partial pressure of waterin the period G.

The difference of results in the reliability tests between thelight-emitting element 7 and the comparative light-emitting element 8 isthought to be due to the difference of conditions at formation of theabove light-emitting layers. This example shows that a light-emittingelement having a long lifetime can be manufactured by application of oneembodiment of the present invention.

This application is based on Japanese Patent Application serial no.2012-105543 filed with Japan Patent Office on May 4, 2012, JapanesePatent Application serial no. 2012-105544 filed with Japan Patent Officeon May 4, 2012, and Japanese Patent Application serial no. 2013-053385filed with Japan Patent Office on Mar. 15, 2013, the entire contents ofwhich are hereby incorporated by reference.

What is claimed is: 1-16. (canceled)
 17. A deposition apparatus comprising: a deposition chamber connected to a first exhaust mechanism and comprising a deposition material chamber in the deposition chamber, wherein the deposition material chamber is connected to a first mass spectrometer and a second exhaust mechanism and comprises a sluice valve and a heating mechanism.
 18. The deposition apparatus according to claim 17, wherein the deposition apparatus is arranged so that an atmosphere in the deposition chamber can be different from that in the deposition material chamber.
 19. The deposition apparatus according to claim 17, wherein the deposition material chamber comprises a mechanism which heats an inner wall of the deposition material chamber.
 20. The deposition apparatus according to claim 17, wherein the deposition material chamber comprises a mechanism which cools an inner wall of the deposition material chamber.
 21. The deposition apparatus according to claim 17, wherein the deposition chamber comprises a mechanism which heats an inner wall of the deposition chamber.
 22. The deposition apparatus according to claim 17, wherein the deposition chamber comprises a mechanism which cools an inner wall of the deposition chamber.
 23. The deposition apparatus according to claim 17, wherein the first mass spectrometer is a quadrupole mass spectrometer.
 24. The deposition apparatus according to claim 17, wherein the deposition chamber is connected to a second mass spectrometer.
 25. The deposition apparatus according to claim 24, wherein the second mass spectrometer is a quadrupole mass spectrometer.
 26. A deposition apparatus comprising: a deposition chamber connected to a first exhaust mechanism and comprising a deposition material chamber in the deposition chamber, wherein the deposition material chamber is connected to a first mass spectrometer and a second exhaust mechanism and comprises a sluice valve configured to separate the deposition material chamber from the deposition chamber and a heating mechanism.
 27. The deposition apparatus according to claim 26, wherein the deposition apparatus is arranged so that an atmosphere in the deposition chamber can be different from that in the deposition material chamber.
 28. The deposition apparatus according to claim 26, wherein the deposition material chamber comprises a mechanism which heats an inner wall of the deposition material chamber.
 29. The deposition apparatus according to claim 26, wherein the deposition material chamber comprises a mechanism which cools an inner wall of the deposition material chamber.
 30. The deposition apparatus according to claim 26, wherein the deposition chamber comprises a mechanism which heats an inner wall of the deposition chamber.
 31. The deposition apparatus according to claim 26, wherein the deposition chamber comprises a mechanism which cools an inner wall of the deposition chamber.
 32. The deposition apparatus according to claim 26, wherein the first mass spectrometer is a quadrupole mass spectrometer.
 33. The deposition apparatus according to claim 26, wherein the deposition chamber is connected to a second mass spectrometer.
 34. The deposition apparatus according to claim 33, wherein the second mass spectrometer is a quadrupole mass spectrometer. 